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SSQL VERSION 3.1 COPYRIGHT (C) 1987-1992 BY STEVE SILVA SILVAWARE P.O. Box 35071 Phoenix, AZ 85069-5071 Special thanks to the hard-working students in CIS425 at the DeVry Institute of Technology, Phoenix, Arizona. ********************************************************************* *** THE LATEST VERSION IS AVAILABLE THROUGH: *** *** The SilvaWare BBS (602) 945-6181 (Details on page INTRO-12) *** *** The SQLBBS (312) 589-0508 (Details on page INTRO-13) *** *** CompuServe in the IBMAPPS forum under Databases *** ********************************************************************* ********************************************************************* *** Do you have a question? I enjoy hearing from you. The *** *** fastest response is by contacting my BBS (see page INTRO-12) *** *** or on CompuServe (73177,2771). You can also contact me *** *** (Steve Silva) by mail. *** ********************************************************************* ********************************************************************* *** IMPORTANT NOTE FOR PRINTERS!!!! *** *** It is assumed that your printer can print the extended *** *** character set. If it can't, the samples of windows and such *** *** won't look the way they should. *** ********************************************************************* ********************************************************************* *** FOR A COPY OF THE ORDER FORM, TYPE: *** *** COPY ORDER.FOR PRN *** *** CREDIT CARDS NOW ACCEPTED. SEE ORDER.FOR FOR DETAILS *** ********************************************************************* ********************************************************************* *** >> UNIX VERSION NOW AVAILABLE!!!!! << *** *** See INTRO-15 for details. *** ********************************************************************* ********************************************************************* *** If you have a PC XT or compatible, SSQL may run too slow. Use *** *** SSQLENG directly. See INTRO-4, WORD-1, SCRIPT-1 for info. *** ********************************************************************* TABLE OF CONTENTS OVERVIEW Enhancements From Earlier Versions.................INTRO-1 The Cost of These Wonderful Things.................INTRO-2 The Future of SSQL.................................INTRO-3 The Components of SSQL.............................INTRO-4 Installation...........................................INTRO-5 Fine-Tuning............................................INTRO-5 Start Up Options.......................................INTRO-5 Quick Start............................................INTRO-6 The Basics of the SSQL Environment.....................INTRO-6 Differences In The Registered Version..................INTRO-7 Permission to copy ....................................INTRO-9 ********LICENSE AGREEMENT - PLEASE READ .......................INTRO-9 SSQL Specifications....................................INTRO-10 Contents of Disk ......................................INTRO-10 dBase Compatibility ...................................INTRO-10 Key Words Needed to Understand the Documentation.......INTRO-11 Syntax Diagrams .......................................INTRO-12 SilvaWare BBS - latest version and support too.........INTRO-12 SSQLBBS - An excellent BBS in the Chicago area.........INTRO-13 UNIX VERSION AVAILABLE!!...............................INTRO-15 The Text Editor........................................ENV-1 Block Commands.................................ENV-1 Cursor Movement Commands.......................ENV-1 Insert & Delete Commands.......................ENV-1 Miscellaneous Editor Commands..................ENV-2 File Open...........................................ENV-2 The File Dialog Box....................ENV-2 New............................................ENV-3 Save...........................................ENV-3 Save As........................................ENV-4 Input..........................................ENV-4 Change Dir.....................................ENV-4 Print..........................................ENV-5 DOS Shell......................................ENV-5 Exit...........................................ENV-5 Edit Undo...........................................ENV-5 Cut............................................ENV-6 Copy...........................................ENV-6 Paste..........................................ENV-6 Show Clipboard.................................ENV-6 Clear..........................................ENV-6 Search Find...........................................ENV-7 Replace........................................ENV-7 Again..........................................ENV-7 Window Size/Move......................................ENV-7 Zoom...........................................ENV-8 Tile...........................................ENV-8 Cascade........................................ENV-8 Next...........................................ENV-9 Previous.......................................ENV-9 Close..........................................ENV-9 SQL Process........................................ENV-9 Form...........................................ENV-10 Report.........................................ENV-14 THE EXAMPLE DATABASE .................................DATABASE-1 USING YOUR OWN WORD PROCESSOR FROM WITHIN SSQLENG.....WORD-1 USING SCRIPT FILES IN SSQL AND SSQLENG................SCRIPT-1 PUTTING COMMENTS IN SCRIPT FILES (OR ANY FILE)........SCRIPT-1 DOS SHELL FROM SSQLENG................................SCRIPT-1 EXTRACTING DATA FROM A SINGLE TABLE...................SELECT-1 Distinct ...........................................SELECT-2 Where ..............................................SELECT-3 search_expression ..................................SELECT-3 Special Search Expression - is null, is not null ...SELECT-5 Special Search Expression - like, not like .........SELECT-6 And, Or, Not .......................................SELECT-7 Any ................................................SELECT-11 In..................................................SELECT-12 All.................................................SELECT-12 Between constant AND constant.......................SELECT-13 Importance of the NULL (Unknown value)..............SELECT-13 Mathmatical Functions Avg, Min, Max, Sum, Count.....SELECT-15 Column Calculations (+, -, *, /) ...................SELECT-18 Group by, Having ...................................SELECT-19 Order by ...........................................SELECT-20 Redirectto .........................................SELECT-21 JOINING...............................................JOIN-1 SIMPLE SUBQUERIES.....................................SUB-1 CORRELATED SUBQUERIES.................................COR-1 CONVERTING ENGLISH TO SQL.............................ENG-1 CREATE A TABLE........................................CREATE-1 CREATE A VIEW.........................................VIEW-1 DROP A TABLE/VIEW.....................................DROP-1 INSERT DATA INTO A TABLE..............................INSERT-1 UPDATE DATA IN A TABLE................................UPDATE-1 DELETE DATA FROM A TABLE..............................DELETE-1 TUTORIAL..............................................TUTORIAL-1 *** OVERVIEW *** SSQL 3.1 is a FULLY-FUNCTIONAL, COMPLETE ANSI SQL implementation with the exception of the security features (GRANT, REVOKE). It has everything else: CREATE SELECT table any not exists view all group by index in having INSERT like order by values not is null w/ select and is not null UPDATE or column calculations (+,-,/,*) DELETE exists aggregate functions DROP (avg,min,max,sum, count) FULL SUPPORT FOR NULLS UP TO 14 TABLES IN JOINS UP TO 14 LEVELS OF SUBQUERIES IT EVEN SUPPORTS CORRELATED SUBQUERIES!!!!! IT CAN DIRECTLY ACCESS ANY DBASE III-COMPATIBLE FILE (without memo fields) ALSO, ANY FILE CREATED THROUGH SSQL CAN BE ACCESSED BY A DBASE III-COMPATIBLE PROGRAM!! INDEXING THAT MAKES JOINS FASTER THAN DBASE OR ORACLE!! MANY ADD-ONS THAT MAKE IT EASIER TO WORK WITH: Integrated Environment with full text editor Form Generator (data entry/update/delete/view) Report Generator Import/Export text files Programmer's interface *** ENHANCEMENTS (PROBLEMS CORRECTED) FROM PREVIOUS VERSIONS *** I have been working on this product off-and-on for five years. User feedback has noted some areas that needed of improvement. I have addressed the following problems in the current version: *1. SSQL 2.3 IS EXTREMELY USER-UNFRIENDLY. DIFFICULT TO MAKE CORRECTIONS. DIFFICULT TO SEE, PRINT, AND SAVE RESULTS. SSQL has a fully-integrated multi-window text editor with full mouse-support. The query is entered in a text window on the left half of the screen and the result is in a text window on the right half of the screen. Either window can be easily saved and/or printed. *2. SSQL 2.3 HAS NO ON-LINE HELP Well, now it does. There is full help for the SSQL environment but only the registered users get the full SQL help. INTRO-1 *3. THE MAJOR PROBLEM WITH SSQL 2.2 HAS BEEN THAT IT IS SLOOOOOOW WHEN LARGE TABLES ARE JOINED. Indexes are now available to increase processing speeds dramatically. Although the shareware version allows you to create indexes, only the version with the index option will process indexes. However, the results are dramatic. I did the following test on an IBM PC AT using the SSQLENG program directly. Results will be slower using the SSQL environment. Time In Seconds To Display Various Queries Number of Rows Joined SSQLENG Oracle 5.1 dBase IV 1.1 100 X 100 5.5 16 38 100 X 100 X 100 10.0 22 39 1000 X 1000 10 rows 3.5 123 24 1000 X 1000 All rows 45.0 157 108 The dBase results could probably be made better by some fine-tuning. Also, the only version of Oracle available to me is an old one. I hope newer ones are faster. My current version implements only the mostcritical aspects of indexing. Indexes are used when testing for equality and when the tests are linked with ANDs. Without indexes, (i.e. the shareware version) SSQL would take MANY hours to join two tables with 1000 rows each. I got tired trying to find out exactly how long. *4. DATA ENTRY IS DIFFICULT AT BEST IN SSQL 2.2. I have included an easy-to-use program that generates data entry screens called FORM. The screens can be easily modified by any text editor. Besides the basic add, update, view, and delete, you can create help screens, cross- reference data in another table, test for ranges, and test for a certain set of data. You can move back and forth from entry to entry and there is full data editing capabilities. *5. REPORT FORMATTING IS PRIMITIVE IN SSQL 2.2. I have included a report generator that does all the basics - subtotals, grand totals, page breaks, page numbering, current date, headings, footers, calculations, etc. INTRO-2 *6. THERE IS NO PROGRAMMING INTERFACE IN SSQL 2.2 Now you can include SSQL in your favorite programming language (including batch files). I have created an extensive command line inteface that I use in the SSQL, SSQLFORM and SSQLRPT programs. The interface allows you to access everything that SSQL can do. You can call it from within C (spawn) or even a batch file. Although I haven't tried it, I assume it will work with Pascal and ` even some dialects of Basic. I also offer the Turbo C source code for FORM and REPORT to show how the calls to SSQL can be integrated into a program. I admit that I am not real proud of the code I produced in version 1.0. I started off with the intention of offering the code so I tried to write it in an easy-to-understand style. Well, as often happens, the problem was a bit more involved than I thought and there are a few kludges here and there. Oh well, it may give you some ideas!! No, I do not offer the source code of SSQL. ** THE COST OF THESE WONDERFUL THINGS ** I have enclosed an order form for your convenience. It is in the file ORDER.FOR. At the DOS prompt type: COPY ORDER.FOR PRN SSQL 3.1 - $35.00 SSQL PRO 3.1 (The version with indexes) $45.00 SSQL PRO + source code for FORM & REPORT + Programmer's Interface $65.00 Shipping is $3.00 USA (Priority Mail) , $8.00 foreign (airmail) ***** FOREIGN CUSTOMERS ***** CHECKS SHOULD BE PAYABLE THROUGH A U.S. BANK. INTERNATIONAL MONEY ORDERS ARE GOOD. SO FAR, I HAVE HAD NO PROBLEM WITH CASH BEING SENT THROUGH THE MAIL. OTHERWISE, USE A CREDIT CARD. *** THE FUTURE *** I have been working on this product for five years with a major upgrade at least every year. Although I refuse to make any promises, this is what I am working on as of July, 1992: INTRO-3 *1. SQL2. There is a new SQL specification that is very complex. I have tried working on it but I have found that I need help in converting the VERY CRIPTIC specifications to algorithms. One person that was going to help me dropped out. If there is anyone out there willing to help, I sure would appreciate it. I need someone who can take the specifications and convert it to a set of test data along with the various operations and the results based on the test data. I realize it is a monumental task. The first thing I would like to work on is the catalog area because this is what users have been requesting. However, I would accept help in any of the many areas in the new specification. I would also like to know if there are any good articles related to SQL2. *2. Extensive on-line tutorial with integrated testing. *3. Use of expanded memory to allow much larger output tables. *** THE COMPONENTS OF SSQL *** There are four components to the SSQL environment. These four components correspond to the four programs: SSQL.EXE - The user-friendly control program SSQLENG.EXE - The SQL engine that does the processing SSQLFORM.EXE - A form generator that makes data entry easy SSQLRPT.EXE - A report generator to create formatted reports * SSQL.EXE * This is the main program that you will typically use to enter your SQL commands. Pressing F4 will take the command and send it to SSQLENG.EXE for processing and the answer will be displayed in an text window. You can also access the form and report generators. A complete help system is included, not only for the editor environment, but also for SQL syntax and examples. You enter commands in a full-featured multi-window text editor. The editor uses the older WordStar(tm) style commands and the newer CUA(tm)- compatible commands that are popular in Windows 3.0 programs. * SSQLENG.EXE * This is the SQL database engine that does all the work. This can be run as an independent program. When you run this, you simply type a command and get a response. The command can be on multiple lines. It is useful when you want to avoid the overhead of SSQL.EXE which limits the output to about 32,000 characters. By using SSQLENG.EXE directly, the limitation increases 10 times to about 320,000. The input file sizes in either case is unlimited. There are some non-standard utilities available when using SSQLENG.EXE directly. See WORD-1 and SCRIPT-1. * SSQLFORM.EXE * This the very basic forms generator for SSQL. It allows data entry, update, delete, view, and browsing on a row by row basis. It can be run from DOS by typing: SSQLFORM <filename> where <filename> is a valid table name. See details in the SSQLFORM section. INTRO-4 * SSQLRPT.EXE * This is a basic report generator which can be run by typing: SSQLRPT <filename> where <filename> is any valid report file. See details in the REPORT section. *** INSTALLATION AND FINE-TUNING SSQL *** The following must (normally) reside in the same directory: SSQL.EXE SSQLENG.EXE SSQL.HLP SSQLEDIT.HLP SSQLENG.ERR SSQLFORM.EXE SSQLRPT.EXE You can set a PATH to the directory that contains the above files. Your data files must reside in your default directory (the directory you are in). You can also put everything in the same directory. *** FINE-TUNING *** When you press F4 to process, SSQL calls the program called SSQLENG.EXE. The result of the processing usually is written to QUERY.TXT. Control is returned to SSQL and QUERY.TXT is read into an edit screen. The speed of this can be greatly enhanced if SSQLENG.EXE is in a RAM disk with at least 150K. Assuming that your RAM disk is D: 1. Copy SSQLENG.EXE to D: 2. Set the environment variable SSQL to D: with the following command: SET SSQL=D:\ Now when you run SSQL and press F4, SSQL will use D: to load SSQLENG, and D: will be used for all temporary files. *** START UP OPTIONS *** SSQL /n Opens a new file (the default) SSQL *.QRY Goes to Open File and displays all the *.QRY files SSQL DEMO.QRY Opens DEMO.QRY in an edit window SSQL /w Opens a new file that is as wide as the screen. It can be used with file names and wild cards. SSQL /l For monochrome LCD screens that do not have highlighting. It may not work on all computers, especially the original (pre-XT) PCs. You can tell it doesn't work by the fact that it locks up. Use /m which is similar. SSQL /m Regular monochrome displays SSQL /b 25-line mode. This will override the automatic 50-line mode for VGA screens. INTRO-5 Any logical combination is OK such as: SSQL /m /w *.QRY *** QUICK START *** At DOS prompt type: SSQL (and press ENTER) Now you are in the SSQL environment. Press ENTER at the Intro screen. Type the command, e.g. select * from branch; Press F4 to process the command. The answer will appear in a edit window on the right. You can now edit it, print it, save it - anything you can do with a regular file. Press F5 to make the query fill the screen. You can now use the standard edit keys to move around the response if it is larger than the screen. If you want a new query, press ALT-F3 to close the output window on the right, otherwise the "desktop" gets cluttered and you will soon run out of space. To erase the previous query quickly, press Shift-PgUp (assuming the cursor is at the end of the query), and Ctrl-Del. The Shift-PgUp marks the entire query, and the Ctrl-Del erases the block. *** THE BASICS OF THE SSQL ENVIRONMENT *** When you first type SSQL, and press ENTER the following appears at the top: File Edit Search Windows SQL and at the bottom: F1 Help Shift-F1 SQL Help F3 Open Alt-F3 Close F4 Process F5 Zoom Since you will usually be using SSQL for entering SQL queries, you will probably have little need for the Edit, Search and Windows options. Most of what you need is along the bottom of the screen. <F1> Virtually everything that follows is already in over 45 help screens that you can access by pressing F1 while in SSQL. To exit help, press ESC. Help screens sometimes have highlighted words and phrases which correspond to additional help screens. You can use the TAB key to move to a highligted area and press the ENTER key to go to that help screen. <Shift-F1> will get you SQL help only if you are using the registered version. INTRO-6 <F3> will take you to the File Open screen (see page ). The default list is *.QRY but you can change it to whatever you want. <ALT-F3> closes a file that is open. It is important to close a file that you are not going to use any more. Every time you process a query, a new file is opened. <F4> processes a SQL statement in the active window (the window where the cursor is). If it is a query, the response will appear on the right side of the screen. If it is another type of statement such as "create table", a message box will appear telling you that the table has been created. <F5> zooms in the active window (makes it fill the screen). Pressing it again makes it shrink back to its original size. This is especially useful if the response to your query is over 40 columns wide. When the response is displayed, press F5 to make it fill the screen. *** DIFFERENCES IN THE REGISTERED VERSION *** ** PROGRAM There is no difference in the registered version except that it has full help for SQL syntax. However, registered users can get a version (for an extra $10) that processes indexes. Indexes can make joins (combining data from different files) 40 times or more faster. ** DISK-BASED DOCUMENTATION (UNREGISTERED USERS) In order to fit everything on a single disk, there is only enough documentation on some commands to explain the basics. However, it does show all the ANSI SQL commands so you can see for yourself that the commands actually work. You do not get documentation on most of the utilities that make working in this environment a bit easier and allow you, for example, to output any query to a dBase file which gives you the ability to customize reports. ** FULL DOCUMENTATION (REGISTERED USERS) Actually, it is much more than just documentation. There are two manuals totaling over 450 pages. It was produced with a desk-top publishing package, printed on a laser printer, and bound. One manual is APPLYING SQL. Besides explaining all the details of syntax, it shows the common constructs used in SQL to make creating your own queries much easier. Much of each chapter is centered around translating English into SQL and how to note peculiarities and ambiguities in English that can cause problems in writing queries. Support is offered through my BBS ((602)945-6181),by mail or through CompuServe (73177,2771). INTRO-7 One of the most complex (and useful) topics in SQL is the correlated subquery. Most authors give you a page or two on the topic. That is not nearly enough for you to be able to use it on your own. My chapter on correlated subqueries is over 40 pages. One good gauge on the quality of a book on SQL is how well it explains the correlated subquery and how well it conveys the importance of the topic. It is an essential part of SQL that opens up various categories of queries that cannot be accomplished any other way. The last chapter on queries is CONVERTING ENGLISH TO SQL. It gives you over 50 pages on approaches to converting English to SQL and dozens of examples. It explains how to break down a sentence in English that simplifies its conversion. Many of the common words used in queries are analyzed. As is often the case with English, the same word in different contexts can significantly change the meaning of the sentence and its conversion to SQL. Much of the chapter explains how to convert sentences with negation which can be VERY tricky. For example, let's anylze the following query: List the purchase dates when all of the following products were purchased: MW, NM, GC. The query, although a bit complex when solving it SQL, is nonetheless rather straightforward. When we negate the query it gets even more confusing (and realistic!!): List the purchase dates when all of the following products were NOT purchased: MW, NM, GC. (if all the products were purchased, skip the date) List the purchase dates when NONE of the following products were purchased: MW, NM, GC. (if any of the products were purchased, skip the date) List the purchase dates when something other than the following products were purchased: MW, NM, GC. Once you see the solutions to these queries you will better understand why SQL is "structured" and it should give you a more critical understanding of English queries. The full chapters on the joins and subqueries have many more examples and detailed explanations. The power of SQL can be TOTALLY lost if the user does not understand the basics of data normalization. Normalization involves the rules for creating tables. If the tables are not organized correctly, SQL cannot be used to its full potential. It is important to note that the topic is discussed with the non-technical end-user in mind. Since there have not been any widely available SQL programs, all the books on normalization tend to be very theoretical and academically oriented. INTRO-8 You also get full information on utilities to delete columns from tables, modify column names, change the width of columns, create tables which are subsets of a current table, etc. *** PERMISSION TO COPY *** Please copy this disk and give it to a friend (or anybody else). However, the following restrictions apply: 1. No changes can be made to the distribution disk, including the documentation. 2. You cannot copy or reproduce the printed manual. *** LICENSE AGREEMENT *** You are given a 60-day license to use SSQL. Anything beyond that is as illegal and unethical as using any commercial software. SSQL is shareware, also referred to as user-supported software. Try it. If you like it and use it, register it. It is well-worth the money. If if doesn't suit your needs, you are not out a lot of money. Shareware is a marketing concept to keep marketing costs down. The savings is passed on to the user. Please help support it. CLASSROOM USE. If SSQL is used in a class, each student must be a registered user. Contact SilvaWare for significant volume discounts. (HEY! It may be a good time discuss ethics with your students!) INTRO-9 *** SSQL SPECIFICATIONS *** Requires only one floppy diskette Minimum Memory 640K, need 510K usable memory for SSQL if you want to use FORM and REPORT Maximum number of columns 128 Maximum length of a row 500 bytes (characters) Maximum number of rows It is limited by the overall size of the output. Under SSQL, the limit is about 64K. If you use SSQLENG directly, the limit is about 320K. The tables on the disk can be larger, you just could not display all the rows and columns at once. Also, you could join multiple large tables as long as the resultant table was not over 320K. This means that the output of a table with rows 100 characters wide could contain about 4,000 rows (about 70 pages of report). Maximum levels of subqueries 14 (reduced by # of indexes in use) Maximum number of tables you can join 14 (reduced by # of indexes) ** CONTENTS OF DISK *** READ.ME - Last minute information SSQL.EXE - The integrated environment SSQLENG.EXE - The database engine SSQLFORM.EXE - The FORM Generator (data entry) SSQLRPT.EXE - The REPORT Generator SSQLENG.ERR - Contains error messages EDIT.FIL - The text file with the location of your word processor - (for use with SSQLENG only!) BRANCH.DBF, PROD.DBF, EMP.DBF, MANU.DBF, SALES.DBF, CUST.DBF, BRANCH.SQD, PROD.SQD, EMP.SQD, MANU.SQD, SALES.SQD, CUST.SQD, - The tables used in the documentation SSQL.DOC - Documentation ORDER.FOR - Order form. type: COPY ORDER.FOR PRN for a printout PRINTDOC.BAT - The batch file to print the documentation RPT1.FRM TO RPT7.FRM - Report formats for the REPORT program *** DBASE COMPATIBILITY *** SSQL creates dBase III compatible files and it can read any dBase file with the following exceptions: No memo data type No field length over 132 A significant difference between SQL and dBase is the ability of SQL to store a null (see SELECT-13 for more information). Even dBase IV cannot store a null. The way I have done it is that character columns are filled with blanks, and numeric columns contain -0 (negative zero). You will never see a -0 when using SSQL, the column value will be blank. This information might be useful if you manipulate files created by SSQL in dBase. INTRO-10 You will notice that every .DBF file created by SSQL has a corresponding .SQD file. This stores information specific to file creation - Not Null and Unique (see CREATE-2 for more information). If you access a dBase file not created through SSQL, the .DBF file is created with Not Null set for every column and no uniqueness constraints. If you change the number of fields in a dBase file after it has been accessed by SSQL, you should delete the corresponding .SQD file. Otherwise, the Not Null and Uniqueness constraints will not be correct. *** KEY WORDS NEEDED TO UNDERSTAND THE DOCUMENTATION *** * SQL - Structured Query Language. A standard method of interacting with a database. It is pronounced "SEQUEL"!! However, over the years I have noticed more and more people saying the letters S-Q-L. * TABLE - A table is typically known as a FILE in other systems. You may ask why they don't just call a table a file. It is because that although normally a table does refer to a specific file, a table can refer to something that spans two or more files. This can be done by "creating a view" (see documentation). If you read a book on relational databases, they will probably refer to a table as a relation. * ROW - A row corresponds to a record or a portion of a record in a file. In relational theory it is called a tuple. * COLUMN - A column is typically known as a field in other systems. In relational theory it is called an attribute. The above names were created to give relational databases a consistent and accurate view of data. EXAMPLE: You may have a TABLE named sales which contains COLUMNs called date, custnum, partnum and quantity. Every time you made a sale, you would add a ROW of data to the TABLE. COLUMNS ----------------------------- | | | | date custnum partnum quantity ------ ------- ------- -------- 880201 8524 AD873 928 <-- ROW 880203 7687 VF8709 87 <-- ROW ---------------------------------- ^ | TABLE INTRO-11 *** SYNTAX DIAGRAMS *** Many chapters begin with a syntax diagram that concisely describes a command and its options. It takes some practice to read them but there are only four basic components: lowercase_letters - they describe something that you must supply. The rules for correctly writing this part of the command follow in the documentation. It may represent a single word, such as the syntax for table_name or a rather complicated series of words that is needed for a column_definition. [ ] - items between square brackets are optional. ... - three dots mean previous item may be repeated. UPPER CASE LETTERS and all other symbols such as '(', ')', ';', '.', and ',' - these must be typed as shown. Although when typing the command, you can use lower case instead of upper case letters. For example, refer to the syntax diagram for creating tables. Since CREATE TABLE is in uppercase, it must always be typed as shown. The items in lowercase such as table_name, column_definition, and uniqueness_constraint must be replaced by information you supply. The rules for forming the phrases required by the words in lowercase will be contained in the chapter. The item called column_definition is repeated. The first occurance is outside of the square brackets which means that it is required. The second occurance of column_definition is within square brackets which means that it is optional. There is a comma after the left square bracket which means that if you add another column_definition, there must be a comma before it. There are three dots after the second occurance of column_definition which means that column_definitions can be more than two column_definitions. Other symbols, such as '(', ')' and ';' must be included at the positions shown in the example. In SQL, spacing and lines make no difference. You can create a table with all the components on a single line or put each word on a separate line. *** The SilvaWare BBS - LATEST VERSION AND SUPPORT TOO *** THE PHONE NUMBER WILL PROBABLY CHANGE IN LATE 1992. I HAVE BOUGHT A NEW HOUSE AND I DO NOT THINK THAT I CAN USE THE SAME NUMBER. WRITE ME A NOTE AND I WILL SEND YOU THE NEW NUMBER. Currently, it will support 1200/2400 bps but by the end of the year I should have support for 9600 and 14400. The phone number is (602) 945-6181. Use the standard settings of 8-N-1. The intro screen of my BBS displays the current version of SSQL so you don't even have to go to the File section. If you have a question, just leave a message for the sysop. INTRO-12 SIGN-ON PROCEDURES If you just want to download something, use the name SSQL USER and the password is SSQL. If you have a question, use your own name when you sign-on and it will ask you a few more questions like where you are from and what you want your password to be. TO DOWNLOAD A COPY Note the exact name of the file on the intro screen. Once you have gotten through the sign-on procedures: Press F to get to the FILES section Press D to download the file Type in the name of the file and press ENTER (It will ask for another name - just press ENTER) What you do next is up to your communications package. I assume that you know something about uploading and downloading. If you don't, practice on a local BBS first. The first file you need to download is PKUNZIP because all files on my BBS (and most others) are "ZIPPED" to organize files, save space, and save time in downloading. I hope to make my BBS a meeting place for people interested in SQL. If you have any interesting information about SQL, feel free to upload it. *** SQLBBS - ANOTHER PLACE TO GET THE LATEST VERSION *** The SQLBBS is a BBS in the Chicago area. It is free to everyone. You can download whatever you want on the first call. It even allows you to use Oracle (the most popular SQL DBMS) on-line. The BBS phone number is: (312) 589-0508 Currently supported baud rates are 9600/2400/1200/300 The following is the fastest way to find and download the most current version of SSQL. It assumes that you are somewhat familiar with BBSs. My comment are in the blocks surrounded by asterisks, the other information is what you see on the screen. ********************************************************************** * WHEN YOU FIRST LOG-IN TO THE BBS YOU WILL SEE THE FOLLOWING MAIN * * MENU. PRESS 'F' TO GET TO THE FILE MENU * ********************************************************************** ------*>>> RBBS-PC MAIN MENU <<<*------ ----- MAIL ---------- SYSTEM ---------- UTILITIES ------ ELSEWHERE --- [E]nter Messages [*]nswer Questions [H]elp (or ?) [D]oors [K]ill Messages [B]ulletins [*]oin Conferences [F]iles [P]ersonal Mail [C]omment to Sysop [*]iew Conf. Mail [G]oodbye [R]ead Messages [I]nitial Welcome [X]pert on/off [Q]uit [S]can Messages [O]perator Page [U]tilities [T]opic of Msgs [*]ho's on * = unavailable [*]Library ---------------------------------------------------------------------- Current time: 07:54 AM Minutes remaining: 42 Security: 5 ---------------------------------------------------------------------- MAIN command <?,B,C,D,E,F,H,I,K,O,P,Q,R,S,T,U,X>! F INTRO-13 ********************************************************************** * AFTER PRESSING 'F', YOU WILL BE AT THE FILE MENU. * * PRESS 'S' TO SEARCH FOR A FILE * ********************************************************************** ------*>>> RBBS-PC FILE MENU <<<*------ -- TRANSFER ------ INFORMATION --- UTILITIES --- ELSEWHERE - [D]ownload file [L]ist files [H]elp (or ?) [G]oodbye [*]ersonal dwnld [N]ew files [X]pert on/off [Q]uit [U]pload file [S]earch files [V]iew archives * = unavailable ------------------------------------------------------------ Current time: 07:54 AM Minutes remaining: 42 ------------------------------------------------------------ FILE command <?,D,G,H,L,N,Q,S,U,V,X>! S ********************************************************************** * WHEN IT ASKS WHAT TO SEARCH FOR, TYPE * * SSQL * * IMPORTANT!!!! MAKE SURE THAT SSQL IS IN UPPER-CASE!!!!! * ********************************************************************** Search for (in file name/desc, wildcards name only, [ENTER] quits)? SSQL ********************************************************************** * THEN IT WILL ASK YOU WHICH DIRECTORIES * * PRESS 'A' FOR ALL DIRECTORIES * ********************************************************************** * Ctrl-K(^K) / ^X aborts. ^S suspends ^Q resumes * UPLD DOWNLD What directory(s) (U)pload,A)ll,L)ist,E)xtended +/-, [Q]uit)? A Scanning Directory DOWNLD for SSQL ********************************************************************** THE FOLLOWING LINE WILL GIVE YOU THE CURRENT VERSION. * IF IT IS HIGHER THAN SSQL31, YOU MAY WANT TO DOWNLOAD IT. * ********************************************************************** SSQL31 ZIP (THE REST IS DATE AND SIZE INFORMATION) End list. R)elist, [Q]uit, or download what? ********************************************************************** * IF YOU WANT TO DOWNLOAD IT, JUST TYPE THE NAME OF THE FILE * * (IN THIS CASE SSQL31.ZIP), AND FOLLOW THE INSTRUCTIONS * ********************************************************************** INTRO-14 *** UNIX VERSION NOW AVAILABLE *** I have ported the SSQLENG portion of the package to SCO Unix. SSQLENG is the SQL engine and can be used directly from DOS. See INTRO-4, WORD-1, and SCRIPT-1 for details. It works exactly the way it does in DOS. It handles multi-user problems correctly too. If it is run with tables that are read-only, you can use the SELECT statement, but INSERT, UPDATE, and DELETE will return an error message. You can only use CREATE in directories where you have access, otherwise it will give you an error message. You can get the shareware version for free by accessing the SSQL BBS and downloading it from the SCO Unix file area. You can also send me $10 and I will send it to you on a 3 1/2" or 5 1/4" DOS disk. DIFFERENCES BETWEEN THE SHAREWARE VERSION AND THE REGISTERED VERSION 1. The shareware version has an obnoxious intro screen that begs for money. 2. The shareware version comes with a 60-day license. Naturally, there is no limit on the registered version. 3. The registered version allows the use of indexing which speeds up joins and subqueries many, many times. 4. The registered version has on-line help. 5. You get a bound, laser-printed manual of over 400 pages which is virtually the same as the one you get with a DOS registration. 6. Registered users can purchase extra copies of the manual for $15. COST OF THE REGISTERED VERSION FOR SCO UNIX Only $100 per CPU plus $3 shipping in U.S., or $8 foreign (airmail). INTRO-15 *** THE TEXT EDITOR *** The commands for the file editor are standard to most editors. You can use the ancient WordStar(tm) commands, or the more modern CUA(tm) commands used on products such as Borland languages and WordPerfect for Windows. Actually it is not 100% CUA but it comes close. Some CUA cominations will not work on the original (pre-XT) PCs and compatibles. ** Block Commands * Mark A Block Move the cursor to one end of the block. While holding down the shift key use the arrow keys to move to the other end of the block. Now it is marked. Or... Begin mark Ctrl-K B End mark Ctrl-K K Mark word Ctrl K T Once a block is marked, you can use the following: Copy Ctrl-K C Move Ctrl-K V Delete Ctrl-K Y or Ctrl-Del Or you can use the edit commands: Ctrl-Ins Copy block to clipboard Shift-Del Cut block and put in clipboard Shift-Ins Paste block from clipboard ** Cursor Movement Commands Character left | Left arrow or Ctrl-S Character right | Right arrow or Ctrl-D Word left | Ctrl-Left arrow or Ctrl-A Word right | Ctrl-Right arrow or Ctrl-F Line up | Up arrow or Ctrl-E Line down | Down arrow or Ctrl-X Page up | PgUp or Ctrl-R Page down | PgDn or Ctrl-C ** Insert & Delete Commands Insert mode on/off | Ins or Ctrl-V Delete line | Ctrl-Y Delete to end of line | Ctrl-Q Y Delete character left | Backspace or Ctrl-H Delete character | Del or Ctrl-G Delete word right | Ctrl-T ENV-1 * Miscellaneous Editor Commands Menu bar | F10 Save and Edit | F2 New File | F3 Close Active Window | ALT-F3 Find | Ctrl-Q F Find and Replace | Ctrl-Q A Repeat last Find/Replace | Ctrl-L Cancel Operation | Esc ** File (Alt-F) The File menu offers choices for opening files, changing directories, and exiting the program. * File-Open (F3) The Open command displays the Open a File dialog box. In this dialog box you select the text file you want edit. The Open a File dialog box contains: The File Dialog Box The File dialog box contains an input box, a file list, a file information panel, the standard button Cancel, one other action button (Open if you selected File Open or OK if you selected Save As...), plus a history list that's attached to the Name Input Box. Name Input Box ⁄ƒ Name ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒø ≥ ≥ ¿ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒŸ The Name input box is where you enter the name of the file to load, or the file-name mask to use as a filter for the Files list box (for example, *.QRY). ENV-2 ⁄ Files ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒø ≥ ≥ ≥ FILENM01.QRY ≥ FILENM09.QRY ≥ ≥ FILENM02.QRY ≥ FILENM10.QRY ≥ ≥ FILENM03.QRY ≥ FILENM11.QRY ≥ ≥ FILENM04.QRY ≥ FILENM12.QRY ≥ ≥ FILENM05.QRY ≥ .. ≥ ≥ FILENM06.QRY ≥ \MOREXAMP ≥ ≥ FILENM07.QRY ≥ \TOURS ≥ ≥ FILENM08.QRY ≥ \ANSWERS.DIR ≥ ≥ ±±±˛±±±±±±±±±±±±±±±±±±±±±± ≥ ¿ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒŸ The Files list box lists the names of files in the current directory that match the file-name mask in the Name input box, plus the parent directory and all subdirectories. ⁄ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒø ≥ C:\TP\EXAMPLES\*.QRY ≥ ≥ HELLO.QRY 52 Jul 14,1990 12:00pm ≥ ¿ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒŸ The File information panel shows the path name, file name, date, time, and size of the selected file. None of the items on this information panel are selectable. ⁄ƒƒƒƒƒƒƒƒƒƒø ≥ [ Open ] ≥ ¿ƒƒƒƒƒƒƒƒƒƒŸ The Open button opens a new Edit window and places the selected file in that window. ⁄ƒƒƒƒƒƒƒƒƒƒƒƒø ≥ [ Cancel ] ≥ ¿ƒƒƒƒƒƒƒƒƒƒƒƒŸ If you choose Cancel, nothing changes and no action occurs, and the dialog box is put away. (Esc always cancels a dialog box, even if a Cancel button does not appear.) * File-New File New opens up a edit box to start entering new information. When you exit, it will ask whether you want to save it to a file. * File-Save (F2) Save the current file. If it is untitled (you selected File-New), you will be asked for a name. ENV-3 * File-Save As... Use the Save As... selection when you want to name an untitled file (you selected File|New), or you want to save a file under a different name. The original file will be left unchanged. The command displays the Save a File dialog box. In this dialog box you can select the file name you want to save it under or enter a new name. For a description of the dialog box, see File Open above. * File-Change Dir... File-Change Dir brings up the Change Directory dialog box, in which you can change the current directory. The Change Directory dialog box consists of an input box, a list box, the standard OK and Help buttons, and two other buttons (Chdir and Revert). ⁄ Directory Name ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒø ≥ ≥ ¿ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒŸ The Directory Name input box is where you type in the path of the new directory. ⁄ Directory Tree ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒø ≥ Drives ≥ ≥ ¿ƒ¬C:\ ≥ ≥ ¿ƒ¬SSQL ≥ ≥ ¿ƒƒTABLES ≥ ¿ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒŸ ENV-4 The Directory Tree list box enables you to navigate directories by using the selecting bar and pressing Enter. If you're using the keyboard, press Enter to make the selected directory be the current directory, then choose OK or press Esc to exit the dialog box. ⁄ƒƒƒƒƒƒƒƒƒƒø ≥ [Chdir ] ≥ ¿ƒƒƒƒƒƒƒƒƒƒŸ The Chdir button changes the current directory once you've selected or typed in a directory name. ⁄ƒƒƒƒƒƒƒƒƒƒø ≥ [Revert] ≥ ¿ƒƒƒƒƒƒƒƒƒƒŸ The Revert button goes back to the previous directory, as long as you haven't yet exited the dialog box. * File-Print Prints whatever is in the current window and then advances to the top of the next page. * File-DOS Shell With the DOS Shell command, you can leave the program temporarily to perform a DOS command or run another program. To return to this program, type EXIT at the DOS prompt. * File-Exit (Alt-X) The Exit command terminates this program. ** Edit (ALT-E) The Edit menu conatins commands to undo the previous edit operation, cut a block of text and put it in the clipboard, copy a block of text into the clipboard, paste the most recent block put in the clipboard, show the clipboard which contains ALL previous blocks put in the clipboard, and clear which clears the block from the screen and does not put it in the clipboard. * Edit-Undo The Undo command takes back the last editing command you performed on a line. ENV-5 * Edit-Cut (Shift-Del) The Cut command removes the blocked text form your document and puts the text in the clipboard. You can then move to another location in your document and choose paste to take the cut text out of the clipboard and put it in your document. The text stays in your clipboard so you can paste it more than once. * Edit-Copy (Ctrl-Ins) The Copy command leaves the selected text intact and places a copy of it in the clipboard. You can then move to another location in your document and choose paste to take the cut text out of the clipboard and put it in your document. The text stays in your clipboard so you can paste it more than once. * Edit-Paste (Shift-Ins) The paste command copies the selected text from the clipboard into the document at the cursor. * Edit-Show Clipboard The Show Clipboard command opens the clipboard window which stores the text you cut and copied from other windows. The currently selected (highlighted) text is the text SSQL uses when you choose paste:. * Edit-Clear (Ctrl-Del) The clear command removes the selected text but does not put it into the clipboard. The cleared text is retrievable with the undo command. ** Search The Search menu contains command to find text in the current file, replace existing text with new text, and search again for text to find or replace. ENV-6 * Search-Find (Ctrl-Q F) The find command displays a dialog box where you enter the text that you want to find. It starts searching where the cursor is to the bottom of the file. If you want to search for the same text again, press Ctrl-L or select Search Again * Search-Replace (Ctrl-Q A) The Replace command combines the Find command with the ability to replace the text it finds with new text. You will be asked to enter the text to find. Remember to press the Tab to get to the entry for the replacement text. Use the SearchAgain option to find and replace the next occurence of text. * Search-Again (Ctrl-L) The Search Again command repeats the last Find or Replace. ** Window (Alt-W) The Window menu contains commands to close, move and perform other window-management commands. Most of the windows in this program have all the standard window elements, including scroll bars, a close box, and zoom icons. For more about windows and their elements, refer to windows. * Window-Size/Move (Ctrl-F5) Choose this command to change the size or position of the active window. * Size If you press Shift while you use the arrow keys, you can change the size of the active window. Once you've adjusted its size or position, press Enter. If a window has a Resize corner, you can drag that corner to resize the window. * Move When you choose Window≥Size/Move, the active window moves in response to the arrow keys. Once you've moved the window to where you want it, press Enter. ENV-7 You can also move a window by dragging its title bar with the mouse. * Window-Zoom (F5) Choose Zoom to resize the active window to the maximum size. If the window is already zoomed, you can choose this command to restore it to its previous size. You can also double-click anywhere on the window's title bar (except where an icon appears) to zoom or unzoom the window. * Window-Tile Choose Window-Tile to tile all file viewers on the desktop. ⁄ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒø ≥ …ÕÕÕÕÕÕÕÕÕÕÕÕ1ÕÕª⁄ƒƒƒƒƒƒƒƒƒƒƒƒ2ƒƒø ≥ ≥ ∫ ∫≥ ≥ ≥ ≥ ∫ ∫≥ ≥ ≥ ≥ ∫ ∫≥ ≥ ≥ ≥ ∫ ∫≥ ≥ ≥ ≥ »ÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕº¿ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒŸ ≥ ≥ ⁄ƒƒƒƒƒƒƒƒƒƒƒƒ3ƒƒø⁄ƒƒƒƒƒƒƒƒƒƒƒƒ4ƒƒø ≥ ≥ ≥ ≥≥ ≥ ≥ ≥ ≥ ≥≥ ≥ ≥ ≥ ≥ ≥≥ ≥ ≥ ≥ ≥ ≥≥ ≥ ≥ ≥ ¿ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒŸ¿ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒŸ ≥ ¿ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒŸ Tiled Windows * Window-Cascade Choose Window-Cascade to stack all file viewers on the desktop. ⁄ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ1ƒø ≥⁄ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ2ƒø ≥≥⁄ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ3ƒø ≥≥≥…ÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕ4Õª ≥≥≥∫ ∫ ≥≥≥∫ ∫ ≥≥≥∫ ∫ ≥≥≥∫ ∫ ≥≥≥∫ ∫ ¿¿¿»ÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕÕº Cascaded Windows ENV-8 * WindowNext Choose Next to cycle forwards through the windows on the desktop. * Window-Previous Choose Previous to cycle backwards through the windows on the desktop. * Window-Close (Alt-F3) Choose Close to close the active window. You can also click the Close box in the upper right corner to close a window. ** SQL * File-Process (F4) The Process command takes the text that is displayed and sends it to the SSQL engine to be processed. If it is a query, the response will be in a text file called QUERY.TXT that is opened to the right of the query. Other commands will have a response in a box to describe what occurred. ENV-9 *** FORM *** The Form program allows you to insert, update, view and delete in a much more user-friendly environment than standard SQL offers. It will generate a standard form for a table that can then be modified - or you can start from scratch. Each column in the table can have a: Help screen Column validation - it exists in another table Column validation - it is within a particular range Column validation - it is within a set of values With the column validation, if a mistake is made, the correct values are displayed on the screen. You have full data editing capabilities and you can easily move from prompt to prompt to make changes. You can even change the colors. You can retrieve rows of information from the form based on simple search criteria and then page through the rows retrieved. The current version is limited to tables with less than 24 rows. However, as an incentive for you to register, only the basics are given to you. The order form is on the last page of the SSQL documentation or you can just print ORDER.FRM. * SUMMARY OF KEYS WITHIN THE FORM * UP/DOWN ARROWS will move you from prompt to prompt. LEFT/RIGHT ARROWS will move you within the prompt as long as there is text. HOME KEY will take you to the beginning of the text. END KEY will take you to the end of the text. INSERT KEY will switch between the insert mode and the overwrite mode. DELETE KEY will delete the character where the cursor is at. PAGEUP (used in Update/View mode) will display the previous row of information. PAGEDOWN (used in Update/View mode) will display the next row of information. ENV-10 ESC will cancel the entry and exit the form program. ENTER will move you from prompt to prompt. At the last prompt, it will accept the form and insert the information into the table. F1 When help has been defined for the form, a window containing the help message will be displayed. F2 Takes the information you have already entered in the form and searches the table for a match. All rows that match are retrieved. You can use the PAGEUP/PAGEDOWN to display the other rows. F4 Displays the column value entered in the previous row. This is useful when, for example, you need to enter the same city over and over. Type the city once. For the next row of information, just press the F4 when you get to the city column. ALT-I Puts you in INSERT mode. ALT-V Puts you in VIEW mode and turns off column validation. ALT-U UPDATEs what is on the screen. ALT-D DELETEs based on what is on the screen. * GENERATING A FORM * In order to more easily explain the commands in the form, let's start by having the form program generate a form for us. To do that: 1. Make sure that the form program is accessable from the directory with your table files. We will be using the CUST table that is on the SSQL distribution disk. 2. Type: form cust (and press ENTER) The form program generates a file called CUST.SCR which describes the form and then runs the form and puts you in the insert mode. Press ESC to exit the form. Now you have a file on your disk called CUST.SCR which looks like: D1 Data Entry for CUST D1 CODE ~~ D1 NAME ~~~~~~~~~~~~~~~ D1 ST ~~ D1 RATING ~~ CO CODE CO NAME CO ST CO RATING TA CUST The first two columns on every line must contain a command. The commands are: ENV-11 D1 This displays information on the screen. Anything you type will appear on the screen EXCEPT the underline. The ~ (til) shows where data entry will occur. Every ~ must have a corresponding CO line which defines the column. The first ~s will be matched with the first CO line, the second ~s will be matched with the second CO line, and so on. The ~s do not have to be as wide as the column is defined. If, for example, the column is defined as being 80 characters, you can have ~s only 30 characters wide. It will create a text window. Although you can only see 30 characters at a time, you can still enter the full 80 characters. CO A single valid column name in the table must follow the CO command. There must be a CO command for every set of ~s that appears in the D1 commands. TA The table name is put here. As for the ordering of the commands, the only thing to remember is that the CO command must follow the corresponding ~s. We could rewrite the cust screen to be any of the following: TA CUST D1 Data Entry for CUST D1 CODE ~~ CO CODE D1 NAME ~~~~~~~~~~~~~~~ CO NAME D1 ST ~~ CO ST D1 RATING ~~ CO RATING D1****************************************************** D1* CUSTOMER FORM * D1* Customer Number ~~ Company Name ~~~~~~~~~~~~~~~ * D1* State ~~ Rating ~~ * D1****************************************************** CO CODE CO NAME CO ST CO RATING TA CUST (The following reverses ST and RATING to show that you do not have to put the columns in the same order as they exist in the table.) ENV-12 D1****************************************************** D1* CUSTOMER FORM * D1* Customer Number ~~ Company Name ~~~~~~~~~~~~~~~ * D1* Rating ~~ State ~~ * D1****************************************************** CO CODE CO NAME CO RATING CO ST TA CUST *** INSERT *** You are in the insert mode when you start the form. Refer to the SPECIAL KEYS section for your options within the form. For a NULL, press the ENTER key without entering anything for the column. Pressing the ENTER key at the last prompt will insert the row into the table. *** UPDATE *** NOTE: The Update will only work on tables where the Unique constraint has been specified. By using the Unique on one or more columns when the table is created, it determines the key for the table. For more information, see the Create Table instructions in SSQL.DOC. There are three basic steps to updating: 1. Press ALT-V to get into the VIEW mode. 2. Retrieve the row you want to update. You retrieve rows by entering data in one or more prompts on the form and pressing F2. It will retrieve all rows that are equal to the data you entered. For example, you want to change the rating on a customer in Arizona, but you forget the exact name. You could move to the ST prompt, type AZ, and press F2. The first customer in AZ would be displayed. You could then use PgUp and PgDn to find the correct customer. 3. Change the data in any of the prompts. If more than one row was retrieved, you can press PageDn to move to the next row. When you have changed the row you want updated, Press Alt-U. *** VIEW *** The only difference between update and view is that in view, no data is changed. 1. Press ALT-V to get into the view mode. 2. Retrieve the row(s) you want to view. You retrieve rows by entering data in one or more prompts on the form and pressing F2. It will retrieve all rows that are equal to the data you entered. For example, if you wanted to view all the customers in Arizona, you would move to the ST prompt, type AZ, and press F2. The first customer in AZ would be displayed. 3. If more than one row was retrieved, you can press PageDn to move to the next row - then PageUp move back a row. *** DELETE *** To delete a row, you follow the steps for updating except at step 3 you press ALT-D to delete the row being displayed. ENV-13 ***REPORT Version 1.0 - The SSQL Report Generator *** *** OVERVIEW *** SSQL Report allows you to produce a formatted report. You use SSQL (or any text editor). Instead of just reading the documentation, it is a good idea to first study and run the examples and then come back to the documentation. As is common with shareware documentation, you need to register in order to find out all the details of operation. *** PROCESS A REPORT *** To process a report, first make sure that SSQL has been installed properly. The tables you reference MUST be in the current directory. Select The Report Option from SQL Menu in SSQL by pressing ALT-Q and then R. A file menu will be displayed with the .FRM files which contain the report files. The files RPT1.FRM to RPT7.FRM have been included on the distribution disk. Make sure that RPT1.FRM is in your current directory along with the DBF/SQD files. Select RPT1.FRM and the result will be displayed on the screen after a few moments (quite a few moments if you are using a floppy disk). It can also be run directly from DOS by typing: SSQLRPT RPT1.FRM ***SYNTAX OF REPORT FILES*** All lines begin with a command. All commands are two characters long. The first character after the command corresponds to column one on the report. The following example shows you a basic report. -- RPT1.FRM (With 3 tables and no indexing, it is slow on an -- old PC) HT SALES REPORT HT HT DATE CUST NAME PROD DESCRIP QTY HT ******** *************** *************** *** DT XXXXXXXX XXXXXXXXXXXXXXX XXXXXXXXXXXXXXX 999 ET**** END OF REPORT **** DC date, name, descrip, qty TA sales,cust,prod WH cc = cust.code and WH pc = prod.code ** COMMENTS (--) Begin a line with two dashes if you do not want it processed by the program. ** PRINTER (PR) If you want the report sent to the printer, the command is PR, and the number after it refers to the printer number. If you do not know the printer number, it is probably 1. ENV-14 It advances to the next page after 59 lines. I made it 59 instead of 66 for those of us with Laserjets. If you do not have the PR command, the report will be displayed on the screen. ** HEADING (HT) (optional) The heading is produced at the top of every page or screen. Headings can contain text, the current date (in both U.S. and international formats), a page number, and you can skip a pre- determined number of lines (good for setting margins). For information on HOW to do all this, register and get the full documentation. ** DETAIL TEXT(DT) The detail represents the placement of information for each row retrieved from the table. The information can be placed on more than one line. It corresponds to the rows requested in the Detail Columns (DC) line. It may contain text, but Xs and 9s have special meaning. X This is used for character data. It will only display the number of characters represented by the number of Xs you have for the column. This is useful when a column may be defined as having 30 columns but you just want to see the first 15. You would simply put only 15 Xs in the position you wanted the column information to be displayed. 9 The 9 represents numeric data. You need to make sure that you have enough 9s for the largest number in the column, otherwise asterisks (*) will be displayed instead. Numeric data can be specially formatted (more on that in the full documentation). ** FOOTER (FT) (optional) The footer is placed at the bottom of every page sent to the printer. It is skipped over if the report is sent to the screen. The options for the footer are the same as the ones for the heading. ** END OF REPORT (ET) (optional) This information appears just once, at the end of the report. The options are that same as the ones for the heading. ** DETAIL COLUMNS (DC) There must be a column for every format described under DT. The format follows the syntax for the select statement in SSQL. This means that you can have calculated columns, aggregate functions - anything that you can put between the word SELECT and the word FROM in a select statement. There can be only one DC line. ** SUBTOTALS (optional) ** Actually, subtotal is a misnomer because you can use any aggregate function (count, avg, min, max, sum) - not just sum. There are three parts to creating subtotals. The first part is the format (1T) which has the same rules as the ones for detail ENV-15 text (DT). The second part determines the group you want subtotaled (1B). The third part (1C) contains the aggregate function(s) that you want in the subtotal. The command sent to SSQL is: SELECT Break Column(s), Subtotals FROM (TA line) WHERE (WH line(s)) GROUP BY Break Column(s); For example: --RPT2.FRM HT SALES REPORT HTCust Prod QTY HT---- ---- --- DTXX XX 999 1T ---- 1T Cust Tot 9999 1T DC cc, pc, qty 1B cc 1C sum(qty) TA sales ** SUBTOTAL TEXT (1T) This is where you describe the format of the subtotal. The rules are the same as the ones for detail text (DT) except that you can only use numeric data (9s). ** BREAK COLUMN(S) (1B) This refers to the column(s) that you want the aggregate functions grouped by. The column(s) must also exist in the Detail Columns (DT). It functions just like the GROUP BY clause. See the manual under the section GROUP BY in chapter 10 for more information on what can be put here. ** SUBTOTALS (1C) This is where you put the aggregate functions that you want displayed in the format you described in the Subtotal Text (1T). You need one aggregate function for every numeric format in 1T. ** GRAND TOTAL (optional) Again a misnomer. You can do more than total a column (sum), you can use any aggregate function. The grand total is displayed once at the end of the report. There are two parts: grand total text (GT) describes the format, and grand total columns (GC) describes the aggregate function that you want displayed. The command sent to SSQL is: SELECT Grand Total Column(s) FROM (TA line) WHERE (WH line(s)) ENV-16 For example: --RPT3.FRM HT SALES REPORT HTCust Prod QTY HT---- ---- --- DTXX XX 999 GT ---- GT Grand Tot 9999 DC cc, pc, qty GC sum(qty) TA sales ** GRAND TOTAL TEXT (GT) This is where you describe the format of the grand total. The rules are the same as the ones for detail text (DT) except that you can only use numeric data (9s). ** GRAND TOTAL COLUMN(S) (GC) List the aggregate function(s) that you want in the grand total. There must be one aggregate function for every numeric format described in GT. ** TABLE(S) (TA) This correponds to one or more tables that you want selected. There can be only on TA line in a report. Anything valid after the first FROM in SQL is valid here. See the manual in chapter 10 and 11 for more information on what can be put here. ** THE WHERE CLAUSE (WH) (optional) Anything valid after the first FROM in SQL is valid here including subqueries with the following exception: You cannot have a GROUP BY or an ORDER BY if you have also specified subtotals. Make sure that the DC, TA, and WH lines go together to form a valid statement as in: SELECT (DC line) FROM (TA line) WHERE (WH line(s)); ENV-17 Some more extensive report formats and hints. --RPT4.FRM (Be patient when running this one. It actually -- contains three queries) -- HT SALES REPORT HT MONOLITH MANUFACTURING HTCustomer Name Product QTY HT--------------- ---------- --- DTXXXXXXXXXXXXXXX XXXXXXXXXX 999 1T ------ 1T The customer total is 99,999 1T GT ------- GT GRAND TOTAL ............999,999 ET ET^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ET END OF REPORT ET^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ DC name, descrip, qty 1B name 1C sum(qty) GC sum(qty) TA sales,prod,cust WH sales.cc = cust.code and WH sales.pc = prod.code --RPT4A.FRM - another way of writing RPT4.FRM HT SALES REPORT HT MONOLITH MANUFACTURING HTCustomer Name Product QTY HT--------------- ---------- --- DTXXXXXXXXXXXXXXX XXXXXXXXXX 999 DC name, descrip, qty 1T ------ 1T The customer total is 99,999 1T 1B name 1C sum(qty) GT ------- GT GRAND TOTAL ............999,999 GC sum(qty) ET ET^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ET END OF REPORT ET^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ TA sales,prod,cust WH sales.cc = cust.code and WH sales.pc = prod.code ENV-18 --RPT5.FRM - Multiple line detail HT SALES REPORT HT HT DATE CUST CODE PROD CODE QTY HT CUST NAME PROD DESCRIP HT ******** *************** *************** *** DT XXXXXXXX XX XX 999 DT XXXXXXXXXXXXXXX XXXXXXXXXXXXXXX DT DC date, cc, pc, qty, name, descrip TA sales,cust,prod WH cc = cust.code and WH pc = prod.code --RPT6.FRM - Projections -- Minor quirk - when you repeat column names as in the DC line -- below, "rename" them by putting a unique identifier after each -- one. HT THE EFFECT OF A PERCENTAGE INCREASE HT IN PERCENT OF DEFECTS HT HT MANU PROD ** DEFECTS ** HT DATE STATE CODE 0% 10% 20% 30% HT -------- -- -- -- -- -- -- DT XXXXXXXX XX XX 99 99 99 99 DC date,mst,code,defects,defects*1.1 d2,defects*1.2 d3,defects*1.3 d4 TA prod --RPT7.FRM Multiple subtotals -- Minor quirk - when you repeat column names as in the 1C line -- below, "rename" them by putting a unique identifier after each -- one. HT Code Defects Qty DT XX 99 99 1T Average 99 1T Total 99 1T Maximum 99 1T Minimum 99 DC code, defects,qty TA prod 1B code 1C avg(defects), sum(defects) c2, max(defects) c3, min(defects) c4 ENV-19 *** THE EXAMPLE DATABASE - MONOLITH MANUFACTURING *** Monolith Manufacturing manufactures and markets high tech products in the western states. There are manufacturing facilities in various states. Products are manufactured in batches at each facility. When the batch is finished an entry is made in the table with the date the batch was finished, the product code, the state where the product was manufactured, the quantity of saleable items and the percent of defects in the batch if that is tracked. Related to the manufacturing table is the product table which simply has the description that corresponds to each product code. The sales portion of the business has as its core the sales table. When a sale is made, an entry is made which contains the date of sale, branch code, customer code, salesperson number, product code and quantity purchased. Related to the sales table are the branch table, the employee table and the customer table. The branch table contains the branch code, the state the branch is in and the employee number of the manager. The employee table contains the employee number, the name of the employee, and the employee's manager number if the employee has a manager (the president does not have a manager). All manager numbers have an entry in the employee number column since all managers are also employees. The customer table contains the customer code, the customer name and the state where the customer resides. The following contains details on the Monolith's six tables. The data types correspond to the types used in the create table command. When a column in one table corresponds to a column (especially a primary key) in another table, it is in the form of TABLE.column. This information will be useful when we need to retrieve information that spans tables. SALES TABLE column data Common columns in name type description other tables date date Date of sale bc char(2) Branch code BRANCH.code cc char(2) Customer code CUST.code sn numeric(2) Salesperson number EMP.code, EMP.mgrnum, BRANCH.mgrnum pc char(2) product code PROD.code, MANU.code qty numeric(3) quantity Key is date, bc, cc, sn, pc DATABASE-1 BRANCH TABLE column data Common columns in name type description other tables code char(2) branch code SALES.bc st char(2) state code CUST.st, MANU.mst mgrnum numeric(2) manager number EMP.enum, EMP.mgrnum, SALES.sn KEY is code EMP TABLE column data Common columns in name type description other tables enum numeric(2) employee number EMP.mgrnum, BRANCH.mgrnum, SALES.sn name char(20) employee name mgrnum numeric(2) manager number EMP.enum, BRANCH.mgrnum, SALES.sn KEY is enum PROD TABLE column data Common columns in name type description other tables code char(2) product code MANU.code, SALES.pc descrip char(15) product description KEY is code MANU TABLE column data Common columns in name type description other tables date date date of manufacture code char(2) product code PROD.code mst char(2) state where product BRANCH.st, PROD.st is manufactured defects numeric(3) percent defects in batch qty numeric(3) quantity manufactured KEY is date, code, ms CUST TABLE column data Common columns in name type description other tables code char(2) Unique customer code SALES.cc name char(15) st char(2) State MANU.mst, PROD.st rating numeric(2) KEY is code DATABASE-2 USING YOUR WORD PROCESSOR You can modify any SSQL command by calling your text editor or word processor from within SSQL. You must first specify which text editor or word processor you are using in a file called EDIT.FIL. The file must contain the path and name of the text editor or word processor. YOU CANNOT CALL A BATCH FILE. The distribution disk contains an EDIT.FIL with the following: C:\PCWRITE\ED The command to start PC-Write is ED and it resides on drive C: in the PCWRITE directory. You can replace the above line with the path and program name of your own. The EDIT.FIL must reside on your default directory. The syntax is: EDIT [file_name]; The file_name is any valid name which will be accepted by your word processor on the command line. For example, if you want to edit MGRORG, you would type: edit mgrorg; As is true with all commands except calling a script file, you must end this one with a ';'. When you exit your word processor/text editor, you will return to SSQL. Refer to the next section to find out how to process the file you just created. There is a special case when you want to edit the last SSQL command that you typed. Every command you type except edit and exit is stored in a file called RUN. To edit the last command entered type: edit run; If your word processor does not allow you to type the file name that you want to edit after the word processor command in EDIT.FIL simply type: edit; WORD-1 CALL SCRIPT FILE A script file is a text file which contains an SSQL command. The script file can then be called from SSQL or SSQLENG and the command it contains will be processed. SYNTAX: @file_name The file_name can be any valid DOS file name. The file must be text only, no special word processing formats allowed. PC-Write or Qedit are excellent choices because they always produce standard text. COMMENTS IN THE SCRIPT FILE (OR ANY OTHER FILE) You can precede a comment by two dashes and from that point to the end of the line will not be processed by SSQL. The comment can be at any place in the line, not necessarily at the beginning as the following example shows. You can create a file called MGRORG which contains: --This query finds the names of managers who have -- salespeople who have sold products to Organomice select name --Get names from emp where enum in (select mgrn --of managers from emp where enum in (select sn -- who have salespeople from sales,cust -- who have sold products to where cc = code -- Organomice and name = 'Organomice')); From SSQL or SSQLENG, you would simply type: @MGRORG Or, from SSQL, use F3 to open MGRORG, and then press F4 to process it. If you do this from SSQLENG, the file you created would be displayed on the screen and then the result would appear. The script file can contain multiple commands. DOS COMMANDS FROM SSQLENG From within SSQLENG, you can type DOS, press ENTER and be in a DOS shell. You can then type EXIT and return to SSQLENG. You can take a short-cut and, for example call Qedit from within SSQLENG to edit MGRORG with the command from within SSQLENG: DOS Q MGRORG At this point you will be in Qedit and be able to edit your query. When you exit Qedit, you will be in SSQLENG and be able to call the script file MGRORG. SCRIPT-1 QUERIES - SINGLE TABLE OVERVIEW The select command is used to retrieve data from tables. The select command is covered in three later chapters too. Although the use of select on a single table is relatively easy, translating from English to SQL (or most other query languages) can be rather tricky. The approach of this chapter is not merely to explain the syntax of the command, it should give you a more critical approach to applying SQL. SYNTAX: SELECT [DISTINCT] column_name [,column_name ...] FROM table_name [,table_name ...] [WHERE search_expression] [REDIRECTTO file_name] <--Non-Standard [GROUP BY column_name [,column_name ...] [HAVING criteria]] [ORDER BY column_name [,column_name ...] If you want all the columns in a table you can replace the list of column names with an asterisk (*). The select command produces a report in the form of a table. Although the basic use of the select takes a short time to learn, the more advanced uses take a long time to master. The tables used in this chapter are on the distribution disk so you can try entering the commands yourself. All the examples have each clause starting on a new line for purposes of clarity. It is not necessary to have them on separate lines. It is sometimes advantageous to keep the query on one line because if you need to make a correction, you cannot backup a line. However, to make correcting command much easier, you can call your word processor from within SSQL. This is described in the full documentation. THE BASICS OF SELECT Find all the data in the manu table. select * from manu; date code mst defects qty -------- ---- --- ------- --- 02/07/87 GC ID 12 15 02/01/87 GC ID 0 55 02/02/87 NM CA 17 93 02/02/87 DD ID 25 02/03/87 DD WA 22 46 02/02/87 NM WA 15 25 02/04/87 DD AZ 12 25 02/04/87 DD CA 15 25 02/06/87 GC AZ 4 43 SELECT-1 Instead of typing all the column names, you can use the * to denote all column names. On the next line, the "from manu" tells us that we want the data to come from the table named "manu". All select commands must end with a semi-colon (;). If we just wanted the product code and the state that it was manufactured in you would type: select code, mst from manu; code mst ---- --- GC ID GC ID NM CA DD ID DD WA NM WA DD AZ DD CA GC AZ 9 rows selected DISTINCT The optional statement "distinct" will eliminate all rows with duplicate columns that you have specified. If you wanted to find out all the different states where products are manufactured, you would type: select distinct mst from manu; mst --- ID CA WA AZ 4 rows selected As you can see only 4 rows were found. This is because there can be more than one row with the same state. Only the first occurrence of each data element is retained. The "distinct" modifier can be used with one or more column names in a select statement. However, the "distinct" modifier operates on the whole row, not just a single column. In the manu table, the primary key is date, code, mst. What if we wanted not only the state where the products are manufactured but the product codes too. Notice what happens with the following: SELECT-2 select mst, code from manu; mst code --- ---- ID GC ID GC CA NM ID DD WA DD WA NM AZ DD CA DD AZ GC Some of the rows are duplicated because it is possible to manufacture the same product in the same state but on a different date. To get rid of the duplication of rows we can add the "distinct" modifier. WHERE The where clause of the select command is the most powerful and complex part of SQL. Our discussion will be broken down into various phases. The first phase is using the where with a single table name. Later you will see it used with multiple tables and you will find that you can even put another select command within the where clause. search_expression The simplest search expression relates a column name to a constant. A constant is an exact value that you enter. All column values are tested against the constant value. If the column name that you are testing is defined as a character, the constant must be enclosed in single quotes or double quotes. The constant you are searching for may not contain a quote. If the column name you are testing for is defined as numeric, the constant is a number without any quotes. You can relate the column name to the constant in the following ways: = equal <> not equal != not equal ~= not equal > greater than less than >= greater than or equal <= less than or equal IS NULL column value is null IS NOT NULL column value is not null LIKE like a pattern NOT LIKE not like a pattern SELECT-3 Find out which customers are in Arizona. select * from cust where st = 'AZ'; code name st rating ---- --------------- -- ------ ZZ Organomice AZ 34 DD QuarkCo AZ 10 2 rows selected Spaces are optional on either side of the "=". You could have typed: where st='AZ'; Instead of single quotes you could have used double quotes: where st="AZ"; In the manu table, the column name "defects" is the percent of defects when the product was manufactured. The statement below shows you how to get a list of all the information for those products with defects over 10%. select * from manu where defects > 10; date code mst defects qty -------- ---- --- ------- --- 02/07/87 GC ID 12 15 02/02/87 NM CA 17 93 02/03/87 DD WA 22 46 02/02/87 NM WA 15 25 02/04/87 DD AZ 12 25 02/04/87 DD CA 15 25 6 rows selected The symbols such as <, >, =, <=, >=, and != can be used with character data too. For example, the statement below shows how to retrieve all customer names alphabetically greater than Machado. SELECT-4 select name from cust where name > "Machado"; name --------------- Technoharps Organomice QuarkCo Marswarp Multicrud 5 rows selected SPECIAL SEARCH EXPRESSION - IS NULL, IS NOT NULL Nulls are an important concept in relational databases. For example, let's look at the percentage of defects in Idaho: select * from manu where mst = 'ID'; date code mst defects qty ------ ---- --- ------- --- 02/07/87 GC ID 12 15 02/01/87 GC ID 0 55 02/02/87 DD ID 25 3 rows selected In Idaho, the batch of MW on 02/07/87 has 12% defects, GC on 02/01/87 has 0% defects but there is nothing listed for DD. This "nothing" is called a null. It does not mean zero or blank. A null means that the data element is unknown. In our case, product DD in Idaho is not tracked for defects like other products. This isn't to say that there are zero defects. It just means we have no entry. If we wanted to look at all products for which we do not track defects, we would use the following: select * from manu where defects is null; date code mst defects qty -------- ---- --- ------- --- 02/02/87 DD ID 25 1 row selected SELECT-5 We could find all the products for which we track defects by using is not null: select * from manu where defects is not null; date code mst defects qty -------- ---- --- ------- --- 02/07/87 GC ID 12 15 02/01/87 GC ID 0 55 02/02/87 NM CA 17 93 02/03/87 DD WA 22 46 02/02/87 NM WA 15 25 02/04/87 DD AZ 12 25 02/04/87 DD CA 15 25 02/06/87 GC AZ 4 43 8 rows selected Null values can be used with both numeric columns and character columns. SPECIAL SEARCH EXPRESSION - LIKE, NOT LIKE An expression with like is used when we want to retrieve data that is similar in some way to another set of characters. The like expression can only be used with character data. This is explained in the full documentation. AND, OR, NOT We can link expressions with ands and ors. If you use an and, both expressions have to be true in order to add the row to the table we are producing. If you use an or, only one of the expressions has to be true. You can use as many ands and ors as you want in a query. The expressions are evaluated from left to right. All the ands are done first, then evaluation starts again from the left and the ors are processed. If you want to reference different column names in a search, the logic as stated in English is typically the same as it is in SQL. Usually there is no confusion between the and and the or unless you are dealing with the same column name. Find all products in Washington with defects over 16%: select distinct code from manu where mst = 'WA' and defects > 16; code ---- DD 1 row selected SELECT-6 Generally, the use of a single and or an or in a where clause is more or less common sense unless you are referring to the same column name. What if you wanted to find all the products manufactured in Washington and Idaho? This has two meanings in everyday English: 1. Out of all the products we manufacture, I want a list of the ones we manufacture in Washington and a list of the ones we manufacture in Idaho. 2. Out of all the products we manufacture, I want a list of each one we manufacture in BOTH Washington and Idaho. We will accept the first meaning in this example. It is interesting to note that we could have also said, "List all the products manufactured in Washington or Idaho." It seems odd that in English "or" can have the same meaning as "and". Even if you don't agree with my interpretation, beware that others do and that it may cause communication problems. In the English version you use the "and" so there is a tendency to always use the "and" in the SQL version too. This would be wrong. The English perspective and the SQL perspective are different. The English perspective often looks at the whole group of items. The SQL perspective looks at one item at a time. To translate Washington and Idaho into SQL we look at it from its perspective. We will look at each item. If that item is manufactured in Washington or Idaho, we will add it to our table. Notice that when we look at it from the SQL perspective, we use the "or" instead of the "and". This not just a quirk of SQL logic, it is common to virtually all data bases. The statement below shows how to find out all the products manufactured in Washington and Idaho: select distinct code from manu where mst='WA' or mst='ID'; code ---- GC DD NM 3 rows selected It is interesting to note what the meaning would be if we used an and instead of an or. Would it tell us every product manufactured in BOTH Washington and Idaho? No, it wouldn't as you can see in the following: select distinct code from manu where mst='WA' and mst='ID'; no rows found SELECT-7 Actually, it makes no sense. How could a state for an individual item be both WA and ID????? But how WOULD you find out every product manufactured in both Washington and Idaho? The search strategy is rather complex and the topic is covered under joining tables and again when we discuss subqueries. In order to express the opposite logic, you use the not but you have to be careful. The statement below shows how to find the products manufactured outside of Washington or Idaho. select * from manu where not (mst='WA' or mst='ID'); date code mst defects qty -------- ---- --- ------- --- 02/02/87 NM CA 17 93 02/04/87 DD AZ 12 25 02/04/87 DD CA 15 25 02/06/87 GC AZ 4 43 4 rows selected Again, we must be careful about how we express the query in English. The query above cannot be translated as: Find the products NOT manufactured in Washington or Idaho. The query above retrieved some products that happen to be manufactured in Idaho or Washington. We really did not care. The only constraint we cared about was the state in which it was manufactured. The query could accurately be translated in fractured English: Find the products manufactured not in Washington or Idaho. By changing the statement to one that requests products not manufactured in Washington or Idaho, we change the words modified by "not" from the states to products manufactured. To find the products not manufactured in Washington or Idaho we must first find the set of all products manufactured in Washington or Idaho: select distinct code from manu where mst = 'WA' or mst = 'ID'; code ---- GC DD NM 3 rows selected SELECT-8 Then we must find all the products in the other states that are not in the above set of three products. We end up with the following which finds that there are not any products manufactured in the other states that are not manufactured in Washington and Idaho. select distinct code from manu where code != 'NM' and code != 'GC' and code != 'DD'; no rows found Well, you may ask, what IS the select statement to find the products not manufactured in Washington or Idaho? Not so fast. Actually, it would require a subquery that is covered in the section on subqueries. If I may digress... I know. Just a few pages into the basics of the select statement and you are ready to give up. Remember, the logic of SQL is not all that difficult. The main problem is that you do not think critically about the meaning of sentences. Much has been written about the problems of communication between humans and computers. Most of the problems are actually caused by the end-user and the "computer expert". I put the burden on the "computer expert" who should know enough about English to note the subtlties and ambiguities of what the end-user is requesting. This is just as relevant for interpreting queries as it is building complete application systems. Meanwhile, back at the ranch... Normally, if a condition is true, we add that row to the table. By using the not, if the condition is false, we add the row to the table. On the first row of the select statement to find products manufactured outside Idaho and Washington, the state is CA. It was selected because it is not equal to WA or ID. Just as we can express the same thought in English more than one way, we can do the same with SQL. We could have written: select * from manu where mst != 'WA' and mst != 'ID'; OR select * from manu where not (mst = 'WA') and not (mst = 'ID'); SELECT-9 What if we would have written or instead of and in the two examples above? Every row would have been selected. No matter what the state is, it would either be not equal to WA or not equal to ID! Remember that whenever you use the not, you must enclose the expression in parentheses. You can have as many ands and ors in a query as you need. What if you wanted all products in Washington and Idaho with defects less than 16%? select * from manu where (mst='WA' or mst='ID') and defects < 16; date code mst defects qty -------- ---- --- ------- --- 02/07/87 GC ID 12 15 02/01/87 GC ID 0 55 02/02/87 NM WA 15 25 3 rows selected We find that only two products are selected. Notice that parentheses enclose the or expression. This is because without the parentheses the and expression would have been executed first. Remember that without parentheses the ands are processed first and the ors are processed next. Not inserting the parentheses would have changed the meaning considerably: select * from manu where mst='WA' or mst='ID' and defects < 16; date code mst defects qty -------- ---- --- ------- --- 02/07/87 GC ID 12 15 02/01/87 GC ID 0 55 02/03/87 DD WA 22 46 02/02/87 NM WA 15 25 4 rows selected The above query is the equivalent of saying, "List all products in Washington and list all products in Idaho with defects under 16%." Another way of stating it is "In looking through all the products, if a product is manufactured in Washington or an Idaho product has under 16% defects, add it to the list." The important concept is that the 16% defects relates to the products manufactured in Idaho, not all products. SELECT-10 SETS (used with constants) Instead of relating items one at a time, we can relate groups of items at once. These groups are called sets. They are enclosed parentheses and the constants are separated by commas. You saw above how you can use =, !=, <, >, <=, and >=. We can expand that concept to include any and all. This chapter has a brief introduction to sets. Sets are the main topic of the chapters on subqueries where instead of using constants in sets, we use select statements. ANY As you will see, the use of the any with constants is simply a short-hand method of writing a series of comparisons with ors. The any may be combined with any of the comparison operators: =any equal to any >any greater than any <any less than any !=any not equal to any >=any greater than or equal to any <=any less than or equal to any Although there are many possible combinations with any, very few are of any use. With constants, the only one that is typically used is =any. Let's rewrite the query concerning all products manufactured in Washington or Idaho: select distinct code from manu where mst =any ('WA','ID'); code ---- GC DD NM 3 rows selected Translated into English it would be: Select the description from the manufacturing table where the state of manufacture is equal to any of the following - WA or ID. We can use numbers too. What if you wanted to know the basic information on products that have a percentage of defects of 12% or 15%? SELECT-11 select date, code, mst from manu where defects =any (12,15); date code mst -------- ---- --- 02/07/87 GC ID 02/02/87 NM WA 02/04/87 DD AZ 02/04/87 DD CA 4 rows selected IN An equivalent to =any is in. The above query could be translated: select date, code, mst from manu where defects in (12,15); The above two queries could be translated into a query without a set: select date, code, mst from manu where defects = 12 or defects = 15; ALL The all can be combined with all the comparison operators just as was seen with the any. The only common use with constants occurs with the !=all which allows us to exclude a set of data. In the following statement we show information on products manufactured outside of Washington and Idaho. select date, code, mst from manu where mst !=all('WA','ID'); date code mst -------- ---- --- 02/02/87 NM CA 02/04/87 DD AZ 02/04/87 DD CA 02/06/87 GC AZ 4 rows selected Although we translated =any as "equal to any item in the set", !=all is usually translated as "not equal to any item in the set". Another way to state the above query is to find products manufactured in a state that is not any of the following - Washington and Idaho. Confusing, isn't it?? Just remember that SELECT-12 !=all is the opposite of =any. This ambiguity in English is related to a riddle I heard Theo ask on the Cosby show: "What two coins add up to 30 cents and one of them is not a quarter?" The answer, of course, is a nickel and a quarter. The nickel is not a quarter which satisfies the rule. Theo was applying a !=any to the set when a typical listener would think that !=all was actually meant. BETWEEN constant AND constant An easy way to select a range of values is use the between/and component of the where clause. The following shows how to find the basic information for products with defects between 12% and 16%: select date, code, mst, defects from manu where defects between 12 and 16; date code mst defects -------- ---- --- ------- 02/07/87 GC ID 12 02/02/87 NM WA 15 02/04/87 DD AZ 12 02/04/87 DD CA 15 4 rows selected Notice that when we use the between, we include the 12 and the 16. Unfortunately, the word "between" can have more than one meaning in standard English. If you say "The treasure is located between San Francisco and Walnut Creek", you would assume that the treasure is not IN San Francisco or Walnut Creek. That is, you would not include the end points - San Francisco or Walnut Creek. If you say "This insurance plan is available for those people between the ages of 18 and 65", you would assume that if you are 18 or 65, you are eligible. That is, you would include the end points. In English, when the word between is used with numbers, the end points are included. In other cases, the end points are not included. Silly, isn't it!! Just remember that in SQL, between includes the end points. SELECT-13 IMPORTANCE OF THE NULL (UNKNOWN VALUE) Now that you understand the basics of how the where clause works, we need to complicate it a bit with considering the unknown value (the null). If the where clause evaluates to TRUE, then the row is displayed, otherwise, it is not displayed. In most non-SQL databases, the where clause only evaluates to TRUE and FALSE. In SQL we have TRUE, FALSE, and UNKNOWN. We can use truth tables to show the relationship. AND |TRUE FALSE UNK OR |TRUE FALSE UNK ---------------------- ----------------------- TRUE |TRUE FALSE UNK TRUE |TRUE TRUE TRUE FALSE|FALSE FALSE FALSE FALSE|TRUE FALSE UNK UNK |UNK FALSE UNK UNK |TRUE UNK UNK NOT ------------ TRUE |FALSE FALSE |TRUE UNK |UNK This can cause some confusing results until you are used to it. For example, there are nine rows in the manu table. However, the two queries below result in a total of only eight rows. select * from manu where defects = 15; date code mst defects qty -------- ---- --- ------- --- 02/02/87 NM WA 15 25 02/04/87 DD CA 15 25 2 rows selected select * from manu where defects != 15; date code mst defects qty -------- ---- --- ------- --- 02/07/87 GC ID 12 15 02/01/87 GC ID 0 55 02/02/87 NM CA 17 93 02/03/87 DD WA 22 46 02/04/87 DD AZ 12 25 02/06/87 GC AZ 4 43 6 rows selected SELECT-14 At first glance you would think that defects are either equal to fifteen or not equal to fifteen. However there is one instance where defects has an unknown value so it is not displayed. Intuitively you may be saying to yourself that since an unknown value is not equal to fifteen, it should be displayed, but that is not the way it works. If you look at both the AND truth table and OR truth table, there is no difference between the false and the unknown since a result of FALSE or UNKNOWN will prevent a row from being displayed. However, in the truth table for NOT, there is a difference. The opposite of unknown is still unknown. AGGREGATE FUNCTIONS - AVG, MIN, MAX, SUM, COUNT All the aggregate functions operate on numeric columns except count which will operate on any columns. SYNTAX: AVG([DISTINCT] column_name) MIN(column_name) MAX(column_name) SUM([DISTINCT]column_name) COUNT([DISTINCT]column_name) SUMMARY AVG - without DISTINCT: The average of all values in a column AVG - with DISTINCT: The average of non-duplicate values MIN - The minimum value in the column MAX - The maximum value in the column SUM - without DISTINCT: The sum of all values in the column SUM - with DISTINCT: The sum of non-duplicate values COUNT - without DISTINCT: the number of column values COUNT - with DISTINCT: the number of non-duplicate column values Notice that some of the functions have the distinct option. This will exclude all rows in the table which have duplicate column values. The follwing two examples show the difference. select count(mst) from manu; CNT(mst) -------- 9 9 rows selected The above query can be translated as: How many rows have values in the mst column? There are a total of 9. This is not very useful because every row is going to have an entry for mst. The answer will always be the total number of rows in the table since the mst column was created with the "not null" constraint. The following query is typically more useful. It answers the question: "How many different states manufacture products?" SELECT-15 select count(distinct mst) from manu; CNT(mst) -------- 4 Typically, when you are using a column name with count, you will modify it with distinct. When querying a table with a multiple part key, all columns will have the possibility of having duplicate entries. This is the case with the manu table with a key of date, code, mst. With such tables, you will modify the column name with distinct. When you query a table that has a key based on a single column, the only column you can be assured of not having duplicates is the key column. If you want to count all the rows in the table, there is a short-cut: select count(*) from manu; CNT(*) ------ 9 At this point, you may ask what use the column name is without the distinct modifier? It is that wonderful concept of the null that has been touched on before and will be discussed in more detail about the other functions. The count function will not count rows that have a null value in the column you are counting. Actually, all the functions skip rows with nulls. In the employee table, not everyone has a corresponding manager number. The entry for employees without a manager is a null (actually only the president doesn't have a manager in this table). The following tells us how many employees have managers. select count(mgrnum) from emp; CNT(mgrnum) ----------- 14 15 rows selected This can be contrasted with the following query. Notice how simply adding the word "distinct" completely changes the meaning of the query to finding how many managers there are in the company. select count(distinct mgrnum) from emp; CNT(mgrnum) ----------- 7 SELECT-16 The functions also can be used with the where clause. The following shows how many batches of product DD are in the table. select count(*) from manu where code = 'DD'; CNT(*) ------ 4 4 rows selected Before we discuss the other functions, let's look at the percentage of defects in Idaho: select * from manu where mst = 'ID'; date code mst defects qty -------- ---- --- ------- --- 02/07/87 GC ID 12 15 02/01/87 GC ID 0 55 02/02/87 DD ID 25 3 rows selected In Idaho, the are three entries: 12, 0, and "nothing". This "nothing" is called a null. Nulls are important in relational data bases. It does not mean zero or blank. A null means that the data element is not relevant in the row. In our case, product DD is not tracked for defects like other products. This isn't to say that there are zero defects. It just means we have no entry. Because there are only two valid entries for defects in Idaho, the functions will not take into account the null data element. The average percentage of defects will be 12/2 = 6, not 12/3 = 4: select avg(defects) from manu where mst='ID'; AVG(defects) ------------ 6 3 rows selected The sum function totals the numeric values in the column(s) requested. Below we sum the number of product DD that has been manufactured. SELECT-17 select sum(qty) from manu where code = 'DD'; SUM(qty) -------- 121 4 rows selected More than one function can be used in a query: select avg(qty), sum(qty) from manu where code = 'DD'; AVG(qty) SUM(qty) -------- -------- 30 121 4 rows selected Except for the group by clause, you cannot retrieve column values and functions based on column values in the same query. COLUMN CALCULATIONS (*, /, +, -) Numeric columns can be used in calculations. The following symbols are used: * = multiplication / = division + = addition - = subtraction The following shows the values if the defects doubled. select code, defects*2 from manu; code defects ---- ------------ GC 24 GC 0 NM 34 DD DD 44 NM 30 DD 24 DD 30 GC 8 9 rows selected SELECT-18 In a calculation, multiplication and division are processed first, then the addition and subtraction. The order of processing can be changed by adding parentheses. Calculations within parentheses are calculated first. More than one column can be used in a calulation and even the same column can be referenced more than once. The column name for the calculation is taken from the first column name however you can rename the column (as shown in the full documentation). The data type for the calculation is based on the first column in the calculation. Calculations can occur also in the where clause but THERE ARE LIMITATIONS. First, expressions are evaluated from left to right (mult & divide not necessarily first). Second, you cannot use parentheses. GROUP BY, HAVING The group by clause is normally used with aggregate functions. It has two operations: 1. It sorts by the column name. 2. The aggregate functions only operate based on the rows that have the same column name. The functions in essence create sub-totals based on the column name. What if we wanted to know the average defects in each state: select mst, avg(defects) from manu group by mst; mst AVG(defects) --- ------------ AZ 8 CA 16 ID 6 WA 18 4 rows selected The column name after the group by must exist on the line with the select. After the select you can only have column names in the group by and aggregate functions - nothing else. You can restrict the group by clause with the having component. In SSQL you are allowed one simple selection that includes the =. <, <=, >, >=, and !=. As with the group by, the column name in the having component must exist in the select clause. If you only wanted a list of states with defects over 10% you would use the following: SELECT-19 select mst, avg(defects) from manu group by mst having avg(defects) > 10; mst AVG(defects) --- ------------ CA 16 WA 18 2 rows selected The group by clause can have up to two fields. This is when you want a group within a group. The group by clause can be used with the where clause. When we found the average defects in each state we could have modified it by excluding product DD. The where clause and the having clause are related. However, the where clause operates on the whole table without regard for the grouping. The having clause operates on the data that has already been grouped. Because of the way the having clause works, most of the time the having clause contains an operation with an aggregate function because that is the basic purpose of the group by clause. ORDER BY The order by clause sorts the output of the table based on the column name(s) listed. The original table is not changed. As with the group by clause, the order by clause can be used with the where clause. For example, the following query will produce a list of manufacturing information sorted by defects for those items manufactured in Idaho. select date, code, defects from manu where mst = 'ID' order by defects; date code defects -------- ---- ------- 02/02/87 DD 02/01/87 GC 0 02/07/87 GC 12 3 rows selected You also can produce a sort within a sort. The following query will produce an ordered list of dates and within each date the state will be sorted. SELECT-20 select date, mst, code, qty from manu order by date, mst; date mst code qty -------- --- ---- --- 02/01/87 ID GC 55 02/02/87 CA NM 93 02/02/87 ID DD 25 02/02/87 WA NM 25 02/03/87 WA DD 46 02/04/87 AZ DD 25 02/04/87 CA DD 25 02/06/87 AZ GC 43 02/07/87 ID GC 15 9 rows selected The order by clause assumes ascending order. You can reverse the order by finding out in the full documentation When there are two columns to sort, one can be in ascending order while the other is in descending order. In the current version of SSQL, you are limited to two sort columns. REDIRECTTO file_name Normally the report that is produced by the select command is displayed on the monitor. However, with the redirectto clause, the report can be redirected to a text file or to the printer. The text file is in standard ASCII text. That is, there are no special characters in it. The file name you give it must not have an extension because SSQL adds the extension ".txt". If you wanted all the Arizona products stored in a file called ARIZ.TXT and you wanted the report sorted by product code, you would use the following query. select * from manu where mst='AZ' redirectto ariz order by code; The output would be stored in a file called ARIZ.TXT on your default drive. To display the file on the monitor, you would exit SSQL and the following at the DOS prompt: type ariz.txt SELECT-21 You also can have the report sent to the printer. Replace the file name with prn or lpt1. Make sure the printer is on when you use this option. UNION The union command allows you to combine output from two or three different select statements. The two select statements must have exactly the same output format - the same number of columns and each column in the corresponding tables must be of the same data type. For the following example, I assume that there are two tables with the same structure as SALES called SALESCA and SALESAZ however it is not necessary that the tables have the same structure, just the output columns. The following statement will get the customer code and quantity from SALESCA for those customers who have purchased over 50 of a particular item. The output will also contain all the customers and corresponding quanitities from the SALESAZ table. The output is sorted by customer code. select cc,qty from salesca where qty > 50 union select cc,qty from salesaz order by cc; SELECT-22 JOINING TABLES Often, the data we need exists in more than one table. In order to extract the data, we need to select the appropriate columns and join the tables. The type of join primarily discussed is called a natural join but for the sake of brevity I will just use the word "join" alone. Whenever we join tables, there must normally be a common column. Hear the common column contains the customer code. It is not important that the column names are different. The important aspect is that they describe precisely the same thing - i.e., they have a common domain. In SQL, the join operation normally has three basic components: SELECT column names - for duplicate names, precede the column name with the table name and a period as in prod.code FROM table names separated by commas WHERE common columns are set to be equal The following shows how to combine the sales information from the sales table and the customer name from cust: select name, pc, qty from sales, cust where cc=code; name pc qty --------------- -- --- Organomice MW 23 Organomice DD 34 QuarkCo AB 2 Marswarp MW 81 Technoharps NM 3 Technoharps MW 41 Technoharps GC 33 Compugorp MW 125 Compugorp MW 947 Compugorp DD 452 Compugorp NM 32 name pc qty --------------- -- --- QuarkCo GC 845 Organomice NM 45 Organomice MW 73 Compugorp GC 127 Compugorp DD 32 16 rows selected MUCH MORE IN THE FULL DOCUMENTATION JOIN-1 SIMPLE SUBQUERIES OVERVIEW In previous chapters, any comparison operation was done with actual values or a column name. Whenever we used the =, !=, <, > , <=, >=, in, all, or any there was a column name on one side and either a column name, an actual value or for the in, all, or any, a set of actual values on the other side. The problem is that often the values on right side of the comparison operation are not known until the query is made. In such cases the right side of the comparison is stated as a separate select command that is called a subquery. The result of the subquery is obtained first and the data is passed back to the previous query. Many queries can be linked together in this way. Another way of looking at it is that often, we need to break down our problem into more than one query. Each query will have its own select. We need subqueries when, in analyzing a problem, we find that we need information from one query before we can process another query. Sometimes we can either join tables or use a subquery. Typically, subqueries retrieve information more rapidly than joining tables. SUBQUERIES WITH =, !=, <, >, <=, AND >= These operators can be used with any subquery that produces a single value. It is commonly used with subqueries that contain an aggregate function. The following shows the customer codes and quantity for those customers who have purchased more of product MW in a single purchase than the total purchased by customer BB. select cc, qty from sales where pc = 'MW' and qty > (select sum(qty) from sales where cc = 'BB' and pc = 'MW'); cc qty -- --- EE 81 AA 125 AA 947 ZZ 73 4 rows selected This method also can be used with any column where we know it can only return a single value. SUB-1 SET EXPRESSIONS - IN In the section on simple select statements, we used any and in with constants (actual values). The true power of the set expressions involves its use in subqueries. We will first compare a join with a subquery. If we wanted to get product codes for all products purchased by customers in California, we could join the SALES table and the customer table. select distinct pc from sales, cust where cc = code and st = 'CA'; pc -- MW 1 row selected Another approach would be to break it down into two queries. We know that we need a list of product codes from the SALES table. The SALES table has customer codes but it doesn't have information on states. Another way to state the problem is that we want all product codes from the SALES table where the customer code is in the set of customers that are in California. find the customers in California. select distinct pc from sales where cc in (select code from cust where st='CA'); pc -- MW 1 row selected THERE IS MUCH MORE IN THE FULL DOCUMENTATION SUB-3 CORRELATED SUBQUERIES OVERVIEW A correlated subquery is a subquery that refers to a table OUTSIDE the subquery. This causes correlated subqueries to be processed differently from simple subqueries. Simple subqueries are processed once, and the result is passed back to the main query. The correlated subquery is processed for every row in the main query. This allows us to process a subquery based on a particular column value in each row of the main query. It can get even more complex with multiple levels of subqueries. With simple subqueries, each subquery is isolated and passes back a single set of values to the previous level. With correlated subqueries, each subquery can depend on more than one of the previous levels. If we are working on the SALES table we can have a subquery that is processed for each customer or product, not the whole table. Another way of looking at it is that for each row in the main query we can take a value, say customer code, and process a subquery based on the customer. The value it produces for the customer can be compared to another value in the same row in the main query. We will do that in the next section when we want to display the complete row in a SALES table for every customer purchase where the quantity purchased is above average FOR THAT CUSTOMER. With a simple subquery we could only compare customer purchases with average SALES for the whole table or a SINGLE customer. Using the correlated subquery is sometimes like being able to compare values to a subquery with a GROUP BY. Often, we just want to test for the existence of a row in a subquery based on a value in the first level of the query so SQL has the exists predicate. By using the correlated subquery we can create some rather complex tests on sets of data. AGGREGATE FUNCTIONS Let's contrast the correlated subquery with a simple subquery that is produced below: select * from sales where qty > (select avg(qty) from sales); date bc cc sn pc qty -------- -- -- -- -- --- 04/01/87 1A AA 10 MW 947 04/08/87 1A AA 10 DD 452 04/08/87 1B DD 11 GC 845 3 rows selected COR-1 It solves the problem for displaying the complete row in the SALES table for every customer purchase where the quantity purchased is above average (based on the complete SALES table). The way a simple subquery works is that it is processed ONCE, and the result is passed back to the main query. Now let's change the query a little bit. Now we want to display the complete row in a SALES table for every customer purchase where the quantity purchased is above average FOR THAT CUSTOMER. Without knowing much else, it should at least be obvious that we need to process the subquery more than once since the query states that we need an average for EACH customer to compare the quantity to. Actually, the correlated subquery is more inefficient than this. Usually, for EVERY row in the first table, the subquery is processed: select * from sales sales1 where qty > (select avg(qty) from sales where cc = sales1.cc); date bc cc sn pc qty -------- -- -- -- -- --- 04/12/87 1B BB 27 MW 41 04/15/87 2A BB 33 GC 33 04/01/87 1A AA 10 MW 947 04/08/87 1A AA 10 DD 452 04/08/87 1B DD 11 GC 845 04/01/87 2A ZZ 12 NM 45 04/08/87 2A ZZ 12 MW 73 7 rows selected On the last line of the subquery we set cc = sales1.cc. This means that for every row in the first table, it will take the customer code (sales1.cc), and compute the average quantity for that customer. It will then determine whether the quantity is greater than the average quantity. We had to use the alias sales1 to distinguish one SALES table from the other. Following any table name we can rename it to avoid confusion or ambiguity. The alias can be any name that would be a valid table name. COR-2 EXISTS/NOT EXISTS The exists predicate tests for the existence of a row selected in a subquery BASED ON DATA IN THE CURRENT QUERY (and possibly outer queries). We do not care what data selected happens to be in the subquery, we just want to know that it exists. The following shows how to find the names of products in the SALES table. select descrip from prod where exists (select * from sales where code = pc); descrip --------------- Megawamp Gigasnarf Nanomouse Dynamic Disk 4 rows selected THE TRUE VALUE OF THE CORRELATED SUBQUERY CAN BE SEEN IN THE FULL DOCUMENTATION - ABOUT 40 PAGES!!! COR-3 CONVERTING ENGLISH TO SQL OVERVIEW The previous chapters emphasized the point of view of SQL and understanding all the parts. This chapter is more concerned with the point of view of a person wanting to solve queries using SQL. There are three pieces of important information - understanding the database, understanding the query, and finally writing the SQL statement. *************************************************************** ** THE FULL DOCUMENTATION HAS THE SQL STATEMENTS AND ** ** EXPLANATIONS. THE FOLLOWING WILL GIVE YOU A GOOD ** ** IDEA OF THE FLEXIBILITY OF SQL AND THE VARIETY OF ** ** PROBLEMS THAT IT CAN SOLVE (IT SHOULD ALSO CONVINCE ** ** YOU TO REGISTER SO YOU CAN GET THE FULL DOCUMENTATION!) ** *************************************************************** UNDERSTANDING THE DATABASE In the chapter on the example databases, when a column was described, any other common columns in other tables was mentioned also. This commonality allows us to work with information that spans tables. There are other ways to group this information that may be useful. The first way is to group them by the common domains. The Monolith Manufacturing database has four basic domains (I do not count date): state, product code, employee number, and branch code. We can group them as follows: NAME TABLES COLUMN NAME STATE CUST st MANU mst BRANCH st PRODUCT MANU code CODE PROD code SALES pc EMPLOYEE SALES sn NUMBER EMP enum EMP mgrnum BRANCH mgrnum BRANCH BRANCH code CODE SALES bc Whenever we join tables or use a subquery, we must use common domains so the above information is essential. ENG-1 GENERAL APPROACH TO SOLVING THE QUERY (This section is only in the full documentation) The Numbering Scheme For Queries Each key word or words is given a number from 1 to 4. The number is further divided into numbers to the right of a decimal as to how the keywords are used. Each example is followed by a letter. Query 3.2B corresponds to the second example(B) for the second use(2) of keyword 3. Queries preceded by an 'N' means that it is a negated version of the query. There may be more than one way to negate it so the version is in the right-most position as in: N3.2B.2. 1 - AND The and is used to refer to information in columns. In its simplest form, it is used to select which columns to display. It is commonly used to determine which rows to display. As you will see from the examples, there are many ways to translate and into SQL. 1.1 Used to describe which columns to display. 1.1A List the date of manufacture, product code, and quantity. 1.2 Used when you need or: 1.2A List the rating for Organomice and Compugorp. 1.2B List the dates of purchase for products MW and NM. 1.3 Ambiguous Solution could be an or a more complex construction. Usually the ambiguity arises because we are referring to sets of values instead of single values. The answer could be a union of the two sets (or) or an intersection (subquery). Query 1.2A asks for rating which will be a single value for each customer. In query 1.3A, we are concerned with two sets of values - products manufactured in Washington and products manufactured in Idaho. Just because it refers to sets of values does not necessarily mean that it is ambiguous. Query 1.2B refers to sets but (in my opinion) it is not ambiguous. Contrast 1.2B with 1.3B which I think is ambiguous. 1.3A List the products manufactured in Washington and Idaho. 1.3B List the dates when products MW and NM were purchased. 1.4. Not Ambiguous However the and translates into a more complex SQL statement. What we are after here is often an intersection of the sets as you can see in 1.4A and 1.4B. That is, we want values common to all sets. An intersection can normally be achieved through a series of subqueries. 1.4A List the products manufactured in both Washington and Idaho. 1.4B List the dates when all of the following products were purchased: MW, NM, and GC. 1.4C List the customers who are from Arizona and have purchased product MW. ENG-2 1.5 Definitely need an and in the where clause. The and is used when we want to test two or more different columns in a row within a single table. 1.5A List the customers who are from Arizona and have a rating over 15. 1.6 Implied and 1.6A List the Arizona customers who have a rating over 15. Same as 1.5A 1.6B List the Arizona customers who have purchased product MW. Same as 1.4C OR 2.1 Normally translates to or: 2.1A List the customer codes for customers who have purchased MW or NM. 2.1B List the customers names for customers who have purchased MW or NM. 2.1C List the customer names for customers who are from California or have a rating less than 10. 2.2 Comparison operators <= and >=. 2.2A List customers who have a rating greater than or equal to 15. 3 - WHICH, WHO, WHOSE, THAT, WITH, WHERE The above words have various meanings but I will emphasize their use in clauses. Clauses connect parts of sentences. Sometimes is makes a query clearer when it is converted to a form that has a clause. The first six queries ask the same thing in different ways. 3.1A Which customers have a rating over 10? 3.1B Who has a rating over 10? 3.1C List customers who have ratings over 10. 3.1D List customers with ratings over 10. 3.1E List every customer whose rating is over 10. 3.1F List every customer where the rating is over 10. Queries 3.1C through 3.1D are the most straightforward because the first part describes what is to be displayed and the second part describes the logic to determine which rows we want. Many of the following can be rewritten in a similar manner but I will usually present only one approach. 3.2 Link tables 3.2A List the customer's states for customers who have purchased products that are manufactured in Idaho. 3.2B Get branch codes for branches that sell products that are sold by branches that sell product DD. This is a rather convoluted one but shows the power of recognizing clauses. Logically we want to find all the branches that sell product DD. ENG-3 Then we want to take those branches and find all the products they sell. With that set of products, we want to find all the branches that sell those products. Notice how in 3.2B each subquery corresponds to each clause. Be careful doing the conversion. Sometimes the "that" does not have to be included. Get branch codes for branches that sell products sold by branches that sell product DD. In the previous sentence the "that" is missing between "products" and "sold". 3.2C List the names of employees who have sold products to Compugorp. 3.2D. Get customer names and product names for customers who have purchased items that are manufactured outside their own state. 3.2E Get branch code, customer names and product names for those who purchase products that are manufactured in their own state from a branch in their own state. 3.2F Get branch numbers for branches that sell to both AA and BB. 3.2G Who are the managers? 3.2H What are the names of managers who actually sold something? 3.2I What are the names of managers whose salespeople have sold products to Organomice? 3.2J What are the names of managers whose salespeople have sold products ONLY to Organomice? We have to add something to exclude salespeople who sold to a customer other than Organomice. 3.2K List the names of Xero Xanadu's subordinates who sold Technowidgits and what were the quantities sold? 3.2L Get branch codes for branches that sell to a Washington or Arizona customer a product manufactured in Oregon. 3.2M Get all pairs of state values where the branch in the first state sells to a customer in a second state. 3.4 Implied that or who The words in parentheses in the following three queries are optional. 3.4A Get product codes for products (that were) sold to any customer in California. 3.4B Get product numbers and corresponding customer names for products (that are) manufactured in the same state as a customer. 3.4C Get customer numbers for customers (who were) sold at least one product from a branch in the same state. 4 - ANY/ALL Translating any and all cause the same sort of problems that were caused by and. This is because the way we use a word in English may be different from the way we translate it to SQL. First of all, I will skip over any queries in which the any or all serve no purpose. Often they are added for emphasis and CAN mean the same thing as in queries 4.1A and 4.1B. Normally, the word any serves no purpose unless it is used in a comparison. ENG-4 4.1 All and any not needed. 4.1A Get all product codes for all products purchased by customers in California. Same as 3.4A 4.1B Get any product code for any products purchased by any customer in California. Same as 3.4A 4.1C Get product codes for products purchased by customers in California. Same as 3.4A 4.2 All used as part of a FORALL quantifier This was discussed in detail in the chapter on correlated subqueries. It is used when we want to compare one set of values to another set of values instead of comparing a single value to a set of values or comparing a single value to a single value. 4.2A Get product codes for products purchased by all customers. 4.2B Get product codes for products purchased by all customers in California. 4.2C Get product codes for products where the minimum defects is greater than 10 and has been purchased by all customers. 4.2C Get customer names for customers who have purchased all products. 4.2D States that manufacture all products sold by a branch in the same state. 4.2E Branches that have sold all the products manufactured in their own state. 4.2F Branches that have sold all the products to all the customers. 4.3 Using any and all in comparisons These are very deceiving. The use of any normally translates to all in SQL or an equivalent construction. This idea is discussed in the chapter on subqueries. 4.3A List products that have defects greater than any defect for products manufactured in Idaho. Compare this to 4.3B. 4.3B List products that have defects greater than all defects for products manufactured in Idaho. Query 4.3A is normally interpreted as the same as 4.3B although logically it means something different. If you think that they are different in common English then I guess SQL has distorted your thinking a bit. When a tennis player says that he is better than ANY tennis player, we assume that he means that he is better than ALL tennis players. The confusion is caused by the fact that in most contexts any and all are very different as in the following two sentences. Give me any book. Give me all the books. 4.3C List products that have defects less than any (all) defects for products manufactured in Idaho. 4.3D List products that have defects the same as any defects for products manufactured in Idaho. In this case we cannot replace the "any" with an "all" and retain the same meaning. ENG-5 N - NEGATION In this section I will take many of the above queries and negate them. N1.2a List the rating for all except Organomice and Compugorp. N1.3A.1 List the products manufactured in neither Washington nor Idaho. N1.3A.2 List the products not manufactured in both Washington and Idaho. N1.3B.1 List the dates that products MW or NM were not purchased. N1.3B.2 List the dates that products other than MW or NM were purchased. N1.4B.1 List the dates when all of the following products were not purchased: MW, NM, and GC. N1.4B.2 List the dates when none of the following products were purchased: MW, NM, and GC. N1.4B.3 List the dates when something other than the following products were purchased: MW, NM, and GC. N1.4C.1 List the customers who are from Arizona and have not purchased product MW. N2.1B.1 List the customers names for customers who have not purchased MW or NM. N2.1B.2 List the customers names for customers have purchased products other than MW and NM. The difference between N2.1B.1 and N2.1B.2 is that the first one would exclude any customer who has purchased MW or NM. The second one would include the customer as long as the customer purchased another product. N3.2A.1 List the customer's states for those customers who have not purchased products manufactured in Idaho. N3.2A.2 List the customer's states for those customers who have purchased products not manufactured in Idaho. N3.2A.2 List the customers' states for those customers who have purchased products manufactured outside (not in) Idaho. The above differs from the previous query in that it will include any product manufactured in Idaho IF it is manufactured outside Idaho. N3.2B.1 Get branch codes for branches that do not sell products that are sold by branches that sell product DD. N3.2B.2 Get branch codes for branches that sell products that are not sold by branches that sell product DD. N3.2B.3 Get branch codes for branches that sell products that are sold by branches that do not sell product DD. The negation is on selling product DD. This is different from saying: "...branches that sell products other than DD". N3.2C.1 List the names of employees who have not sold products to Compugorp. N3.2D.1 Get customer names and product names for customers who have purchased items not manufactured outside their own state. N3.2D.2 Get customer names for customers who have not purchased items manufactured outside their own state. ENG-6 N3.2D.3 Get customer names for customers who have only purchased items in their own state. At first glance N3.2D.3 seems the same as N3.2D.2 but N3.2D.2 would display customers who have not purchased anything. We have to add some more to make sure that the customer actually made a purchase. N3.2F.1 Get branch codes for branches that do not sell to both AA and BB. N3.2F.1 Get branch codes for branches that sell to neither AA nor BB. N3.2F.1 Get branch codes for branches that do not sell to AA or BB. N3.2G.1 What are the names of managers who did not sell anything? N3.2I.1 What are the names of managers whose salespeople have not sold products to Organomice? N3.2I.2 What are the names of managers whose salespeople have sold products to everyone except Organomice? This becomes a tough one because the opposite of "only Organomice" in 3.2I is "everyone except Organomice" and "everyone" corresponds to the FORALL quantifier covered in the chapter on correlated subqueries. The core of this query has to do with "salespeople selling to ALL customers (except Organomice)". N3.2L.1 Get branch codes for branches that sell to a Washington or Arizona customer a product not manufactured in Oregon. N3.2L.2 Get branch codes for branches that sell to a Washington or Arizona customer a product manufactured outside of Oregon. N4.2A.1 Get product codes for products not purchased by all customers. N4.2A.2 Get product codes for products purchased by none of the customers. N4.2D.1 States that do not manufacture all products sold by a branch in the same state. N4.2D.2 States that manufacture no products sold by a branch in the same state. N4.2E.1 Branches that have not sold all the products manufactured in their own state. N4.2E.2 Branches that have sold none of the products manufactured in their own state. N4.2E.3 Branches that have sold all the products not manufactured in their own state. N4.2E.4 Branches that have sold all the products manufactured outside their own state. ENG-7 CREATE TABLE OVERVIEW The CREATE TABLE command is used to create a table file. You can control the contents of the columns in two ways. You can prevent a column from being null and you can make sure that a column or set of columns never contain duplicate values. These restrictions allow us to maintain valid primary keys when we use the INSERT command to add rows to a table or the UPDATE command to modify values in a table. SYNTAX CREATE TABLE table_name ( column_definition [, column_definition...] [, uniqueness_constraint] ); EXAMPLE: The statement below shows how to create the cust table that the documentation uses. create table cust ( code char(2) not null unique, name char(15) not null, st char(2) not null, rating numeric(2) ); You can define up to 27 columns in a table. As with all SQL commands, they can be in uppercase or lowercase. After the name of the table, parentheses enclose the column definitions. The column definitions are put on separate lines to aid in readability. SQL never requires anything to be put on separate lines or have specific spacing. Note that all column definitions except the last one has a comma after it. The above command states that there will be four columns in the cust table: code can have up to two characters. It is the primary key so nulls will not be allowed and each code will be unique. name can have up to fifteen characters. It must contain a value. st is the state postal code and it can have up to 2 characters. It must contain a value. rating is the customer rating. Since NOT NULL is not specified, the customer rating is optional - it does not have to be entered. CREATE-1 COMPONENTS OF CREATE TABLE table_name A table name can be from 1 to 10 characters. The first eight characters must be unique. The first character must be a letter of the alphabet. The rest can be letters or digits, _ (underscore), or #. The table files are created on the disk as in table_name.DBF and table_name.SQD. For example, the cust table, created above would be stored as CUST.DBF and CUST.SQD on your disk. However, from SSQL, you would always refer to it as CUST. Since SSQL adds the extension of DBF and SQD to all table files, you must not use a period in your table name. column_definition column_name data_type [NOT NULL [UNIQUE]] column_name A column name can be from 1 to 10 characters. The first character must be a letter of the alphabet. The rest can be letters or digits. In creating column names remember that when you display a table, the full column name is displayed too as the heading. Long column names tend to fill the screen (or printer) very rapidly when you want to display many columns. The column name is displayed exactly as you type it, retaining the uppercase and lowercase letters. The create statement above created the column names and hence the headings in lowercase letters. We could have written it as shown below. create table cust ( CODE char(2) not null unique, NAME char(15) not null, ST char(2) not null, RATING numeric(2) ); With the statement above, whenever we display data from the table, the headings would in uppercase. data_type The data types in SQL fall into two broad categories - numbers and characters. Within the numbers category, there are exact numeric types and approximate numeric types. However, all numeric data types are converted to the dBase numeric data type. The other types are included to maintain compatibility with ANSI SQL. Two non-standard data have been added to maintain compatibility with dBase - Date and Logical. CREATE-2 Numeric (Exact Numeric) NUMERIC[(length [,decimal_places])] DECIMAL[(length [,decimal_places])] DEC[(length [,decimal_places])] INTEGER INT SMALLINT (Approximate Numeric covered in the full documentation) When you use numeric data types the values are always right-justified (values are pushed to the right so all the decimal lines up). Data must be of this type in order to use any of the numeric functions such as avg, max, min, and sum. The first three data types in the exact numeric category - NUMERIC, DECIMAL, and DEC, can be used interchangeably. It sounds a little odd that a data type called DECIMAL does not necessarily mean that the contents of the column will contain a decimal place since the modifier decimal_places is optional. length (optional) The length of the column be up to 12 digits (including the decimal place. Without this specification, the length is 1. decimal_places (optional) The number of places to the right of the decimal. For Example: cost numeric(5,2) This would allow a maximum of 99.99 to be stored in the column. This also could be defined as: cost decimal(5,2) or cost dec(5,2) It is allowable to use whole numbers even though you define it as having decimals. For example, you want to enter grades that are from 0 to 100 but when you calculate grade averages, you want it calculated to one tenth of a grade point. You would define the column as: grade numeric(5,1) You would enter the grades as whole numbers but when the average is calculated, the decimal would be included. With NUMERIC, DECIMAL and DEC, if you omit the dec_places modifier, the result is a whole number. Data types such as INTEGER (which is the same as INT) and SMALLINT have lengths associated with them. The ANSI standards state that the lengths shall be determined by the implementor so I have picked lengths of ten and five respectively. CREATE-3 INTEGER is the same as numeric(10) or decimal(10) or dec(10) SMALLINT is the same as numeric(5) or decimal(5) or dec(5) You can see that although there are six exact numeric data types, you only need one. Characters CHARACTER[(length)] CHAR[(length)] These data types can be used for any column that you do not use in a calculation. Although the data is usually a combination of alphabetic and numeric data, it is alright if the column just contains digits. The characters are left-justified. The maximum column width is 80. CHARACTER and CHAR can be used interchangeably. If you omit the length modifier, then the length of the column is one. Date DATE The DATE data type creates a column of 8 characters. Dates are entered as mm/dd/yy. Logical LOGICAL - A one character column that can store Y, y, N, n, T, t, F, f, or ? NOT NULL This modifier to a column definition will ensure that there is always a value for this column. It prevents the INSERT and UPDATE commands from allowing a column to contain a null value. When used with the UNIQUE modifier, it is used to specify a primary key. There are special commands to retrieve rows that only have null values in a particular column or to exclude rows that have null values in a particular column. UNIQUE This ensures that each value in the column is unique. If an attempt is made to enter a duplicate value when inserting a new row, an error results and the row is not added to the table. If you use unique, it must be used with NOT NULL. This is typically used when a single column is a primary key. Uniqueness_constraint (covered in full documentation) CHECKING THE STRUCTURE OF A TABLE In order to display the create command used to create the table, type STRUCT followed by the table name. CREATE-4 CREATE A VIEW OVERVIEW A view is a derived table. A view describes an alternative access to columns and tables that already exist. The create table command allowed us to create a physical table that is also called a base table. With a base table every column corresponds to the source of data. We can always use the insert, update, and delete commands on base tables. Views never exist as permanent tables. Whenever you query a view, it creates a temporary table based on your view. When the query is complete, the temporary table is erased. The view can reference an existing column under a different name or keep the original name. The view can be based on more than one table. You can reference as few or as many columns you want in the tables you select. SYNTAX CREATE VIEW view_name [(column_name [,column_name...])] AS select_statement EXAMPLES: Create a view which only shows less than the full number of columns in a table. In a commercial database system, this can be used to prevent users from seeing sensitive data. For example, The employee table may include salary information. A view of that table could have everything except the salary information. It is necessary to have some background in the use of the select command before attempting to create a view of a table. The statement below shows the creation of a view called custa. It is based on the cust table that has four columns: code, name, st, and rating. create view custa as select code, name, st from cust; The column names are the same as they are in the original table. The only difference is that rating is not part of the view. When you use view custa in a query, it acts just like a regular table. When it displays all the columns as shown below, you only see the three columns specified in the view. select * from custa; code name st ---- --------------- -- AA Compugorp WA BB Technoharps OR ZZ Organomice AZ DD QuarkCo AZ EE Marswarp CA FF Multicrud NV VIEW-1 We have no access to the rating column when using the custa view. RULES FOR USING VIEWS It is used in a select statement, NOT an insert, update, or delete statement. To erase the view, use the drop view statement. Can contain any select statement except one that has redirectto. Views should only be used when they are absolutely needed. They can add much confusion to a database design because it is easy to forget which are tables and which are views. (MORE IN THE FULL DOCUMENTATION) VIEW-2 DROP TABLE/VIEW OVERVIEW The drop command is used to erase a table or view from the disk. The drop table command is used to erase the description of the table from the disk. The drop view command erases the view but can never alter data or tables since the view simply describes access to a table or tables. SYNTAX DROP TABLE table_name; or DROP VIEW view_name; EXAMPLES: drop table cust; drop view custa; COMPONENTS OF THE DROP COMMAND table_name The table_name must be a valid table name which contains NO data. In order to delete all the data you can first type: delete from table_name; The delete command erases the data and the drop table command erases the column descriptions. view_name The view_name must be a valid view name. Since no data is affected it can be used at any time. DROP-1 INSERT DATA INTO A TABLE OVERVIEW The ANSI standards define two ways to add data to a table. One requires us to type each value for each column in each row. The other copies data from one table and puts it in another. It is very useful for making corrections to tables. I only describe the first type in this documentation. Registered users find out about the more advanced use of the insert command and a special, non-ANSI command which makes inserting data MUCH easier. Both insert commands maintain the restrictions we may have imposed through the CREATE TABLE command. We could have specified NOT NULL and UNIQUE to prevent certain types of data errors in our tables. INSERT VALUES - SYNTAX INSERT INTO table_name [column_name [,column_name...]] VALUES (column_value [,column_value]); EXAMPLES: The first example shows the typical way to use the insert command since it does not reference any column names. The insert command assumes that you will enter the data in the order that they were created in the table. The second example shows that column names can be referenced. The third example shows that the data entry does not have to be in the order in which the columns were created. Compare the order of the values to the first example. insert into cust values('AA','Compugorp','WA',20); or insert into cust code, name, st, rating values('AA','Compugorp','WA',20); or insert into cust name, code, rating, st values('Compugorp','AA',20,'WA'); MORE DETAIL ON THE COMPONENTS OF THE SYNTAX table_name Any existing table in your database. column_name Normally column names are not used with the insert command. This is because the insert command assumes that we are going to insert values for all the columns in the table in the order in which they were created. You saw this in the first example. It has the same effect as the second example. In the third example we want to insert data in a different order. This could be useful if the source document that we are getting the data from presents the data in a different order from which the table was designed. INSERT-1 column_value There are three types of column values: character, numeric and null. Character data Character data must be enclosed in quotes or apostrophes. The first example above could have been entered as: insert into cust values("AA","Compugorp","WA",20); Although you can enter SQL commands in uppercase or lowercase, care must be taken when entering character data since everything is stored exactly as entered. This can create problems when we are retrieving data. Let's assume that Compugorp purchased some Megawamps so we insert the following information into the sales table: date, branch code, customer code, employee number, product code and quantity. insert into sales values('04/01/87','1A','aa',10,'MW',947); Although SQL would accept the above insert command, we made a critical logical error. The correct customer code for Compugorp is 'AA', NOT 'aa'. This is an error that is rather difficult to detect. Any time we relate the sales table with the cust table, the above row in the sales table will not be retrieved. This could cause reports to disagree. The section on correlated subqueries explains how to detect this problem. Technically, it is called referential integrity. Another mistake that is easily made involves accidentally having leading or trailing spaces in a character value. If we inserted the data for Compugorp with the following: insert into cust values('AA','Compugorp ','WA',20); You will notice the space after the last 'p' in Compugorp. There will not be a problem with it until you try a query that includes the name of the company as shown below. select * from cust where name = 'Compugorp'; The row with Compugorp will not be found because the query did not contain the space after the last p! This is a very frustrating error as I have seen quite a few students accuse me of having a serious malfunction in my program with the look on their faces suggesting what I could do with SSQL. All columns have a particular length associated with them. This denotes the maximum number of characters that the column can contain. When we created the cust table, the name column was defined as char(15) which means that the maximum number of characters it can contain is 15. If more than 15 characters are in the name, only the first 15 are saved. INSERT-2 insert into cust values('GG','Bizzlesnarf & Sons','CA',10); Although the above command would be allowed, when we retrieve the customer name, only "Bizzlesnarf & " would be displayed. Numeric Data The basic rule to remember with numeric data is not to enclose them in quotes as we can see above with the entry for rating. The length of the column as specified in the create table command must not be exceeded. Rating was created as numeric(2) which means that the maximum number of digits is 2. The following insert command would cause an error because the entry for rating contains 3 digits instead of 2: insert into cust values('AA','Compugorp','WA',123); Because of the error, none of the values would be added to the table. Null data I really should not write "null data" or "null value" because the concept of the null means absence of a value. If we add a customer that has no rating we would do something like: insert into cust values('HH','MagnaMice','AZ',null); There are NO QUOTES enclosing the word null. Like all other keywords in SQL, it can be in uppercase or lowercase letters. The null is different from a 0 (zero) in that a null means that there is no rating. A 0 (zero) means that there IS a rating and the rating is 0. This idea is further developed when discussing data retrieval in the section on the select command. INSERT-3 UPDATE DATA IN A TABLE OVERVIEW The update command is used to change column values in existing rows based on criteria in a search_condition that is accomplished through a where clause. If there where any constraints put on the column values when the table was created such as not null or not null unique, the update command makes sure that the constraints are maintained before the columns are actually updated. Next to the insert command, it is the most cumbersome to use. To make updates a bit easier, I made a non-ANSI command which is fully explained in the full documentation. UPDATE SYNTAX UPDATE table_name SET column_name = value [, column_name = value...] WHERE search_condition The value can be a mathmatical expression. EXAMPLES: In the first example, the rating for customer AA is increased by 5. update cust set rating = rating + 5 where code = 'AA'; In the example below, the rating for customer CC is changed to a null. update cust set rating = null where code = 'CC'; The example below shows how to change the percent defects to 10 for a batch of product GC that occurred on July 21, 1987 in Idaho. update manu set defects = 10 where date = '07/21/87' and code = 'GC' and mst = 'ID'; In the following, two columns are changed. For customer BB, rating is changed to 14 and the state column is changed to Idaho. update cust set rating = 14, st = 'ID' where code = 'BB'; UPDATE-1 The example below is a bit more involved. We want to change the rating of branch 2A customers who have purchased above average quantities (overall) to 30. The use of the select command in a where clause is covered in a later section. update cust set rating = 30 where code in (select distinct code from cust, sales where cc=code and bc='2A' and qty > (select avg(qty) from sales)); COMPONENTS OF UPDATE table_name Any existing table in your database. column_name Any valid column name in the table name accessed, including the column(s) which form the key. value The value is anything appropriate for the data type of the column. Any value that would work with the insert command will work with the update command. As with the insert command, the word null is valid to show that there is no value for the column. Remember to put quotes around character values. search_condition The section on the select command has more detail on the search_condition that is accomplished with the use of a where clause. Typically, you want to update a single row. To update a single row the search_condition must test for the primary key so that will be explained here. The primary key allows you to uniquely define each row. The cust table, which is used in most of the examples above, has a primary key based on code. That is, based on the value in code, we know only a single row will be updated. Compound keys are discussed in the full documentation. UPDATE-2 DELETE ROWS FROM A TABLE OVERVIEW The delete command deletes rows based on the criteria in the where clause. Without a where clause, all the data in the table is deleted. Refer to the section on the select statement for details on the where clause. The basic difference between the select * and the delete is that with select, the rows are displayed, and with delete, the rows are deleted. Because of this, it is a smart idea to use the select before you use the delete so you can see the rows that you are going to delete. You can only delete complete rows. If you want to delete column data within a row, use the update command. SYNTAX DELETE FROM table_name [WHERE search_expression] EXAMPLES: The following shows how to delete all the data from the cust table. delete from cust; The following shows how to delete customers from the cust table whose rating is less than 10. delete from cust where rating < 10; COMPONENTS OF DELETE table_name Any existing table in your database. search_condition The section on the select statement has more detail on the search_condition that is accomplished with a where clause. A simple example is shown above. The command to delete customers whose rating is less than 10 could create some problems if there were customers in the sales table with customer codes that you deleted. Whenever you delete a row that contains a primary key that is used in another table, problems can arise. In order to determine whether there are any of those customers in the sales table, you could use the select command as shown below. select * from sales where cc in ( select code from cust where rating < 10); DELETE-1 To delete all the corresponding rows in the sales table for customers whose rating is less than 10, you would simply take the statement above and replace the "select * from" with "delete" as shown below. delete from sales where cc in ( select code from cust where rating < 10); The delete command below shows how to delete all rows in the sales table that do not have a corresponding customer code in the cust table. The not exists is covered in the full documentation. delete from sales where not exists (select * from cust where code = cc); HOW TO RESTORE DATA YOU HAVE JUST DELETED Type it in again!!! (Therefore be very careful when you use this command). DELETE-2 TUTORIAL OVERVIEW This tutorial will take you through the basics creating a tables, inserting data into a table, updating rows in a table, deleting rows from a table, retrieving data from a table, creating a view of a table and dropping a table. It is designed to give you a feel for the types of things that SSQL can do. The detailed description of the syntax is in the main section of the documentation. START SSQL From the DOS prompt type SSQL and press ENTER. There will be a Title screen. The next key you press will be part of the next action so let's first explore the help screens. The shareware version has full help for the editor. The version for registered users adds full help for SQL syntax and examples. CREATE THE TABLE Before we can put any data into the table, you need to describe the type(s) of data that it is going to contain. Often the table we create is referred to as a base table. Base tables contain actual data which is distinguished from a derived table (see Create a View). It is assumed that you have already read the introduction which contains the basic definitions of columns, rows, and tables. You will create a shortened version of a payroll table. For each employee you will store the last name, the first name, salary, and city. The key will be a combination of last name and first name. Type the following: create table pay ( code char(2) not null unique, last char(15) not null, first char(15) not null, salary numeric(5), city char(12), tot_sold numeric(7,2) ); The employee code is up to two characters long and is the primary key so we are telling it that there must be a value for this column (not null) and each one must be unique. Last name and first name can each be up to fifteen characters in length. The values for city are limited to twelve characters. Salary is limited to five digits which means up to $99,999. Total items sold is limited to $99,999.99. You can edit the above description until it is correct. Once it is correct press: F4 This will process the command. If you have correct syntax, there will be a message box in the middle of the screen stating Table Created Otherwise an error message will appear and you can go back and correct it. TUTORIAL-1 At this point we can either save what we just typed or delete it and type something new. Let's delete this one and save the next one. What we want to do is quickly delete all the text on the screen. In editor terms, we want to delete a block of text. Let's find out how to do it by looking it up in the help screens. TO ACCESS THE ON-LINE HELP Let's assume that you want to find help on marking and deleting blocks of text. Press F1. You will notice the following list with the first item highlighted: Quick Start for SQL Commands Text Editor File Edit Search Window SQL Since marking and deleting text refers to the text editor, press the TAB key once to highlight "Text Editor" and press the ENTER key. The next screen gives some basic information but we want information specifically for blocks. It is the first item so it is already highlighted. Press ENTER. It starts with a description of how to mark a block: "Move the cursor to one end of the block. While holding down the shift key, use the arrow keys to move to the other end of the block. Now it is marked" In about the middle of the screen, it gives you more than one way to delete a block: Ctrl-KY, Ctrl-Del, or Del. The reason there is more than one way is to cover a variety of standards. Press ESC to get out of the help screen. Assuming that the cursor is at the end of the command, you can delete the command to create the table by pressing: Shift-PgUp, Del (What it actually does is mark all the text and then you delete the block you marked) Let's create another table which will be need to make joins and subqueries. Type: create table trans ( trans_code numeric(3) not null unique, sales_prsn char(2) not null, prod char(2) not null, qty numeric(3) not null, cost numeric(5,2) not null ); TUTORIAL-2 Notice that the window is untitled (top center of the window). Let's save it under the file name TRANS.CR. Do the following: ALT-F <-this means hold down the ALT key and press F Now you are looking at the File screen. The 'a' in "Save As" is highlighted so press the A key. A file name box appears. Type the following and press ENTER: TRANS.CR Now at the top of the window, the name of the file is TRANS.CR. We want to start a new window. To keep our "desk-top" clean, we should close the existing window before openning a new one. Press ALT F3 to close the window. To open a new window press ALT-F to get to the file menu and press N to open a new file. Now it is time to put data into the table. I offer two ways to do it. Adding data to a table in standard SQL is very cumbersome so I have created a "Form" program to make it easier. For the PAY table I will use standard SQL. For the TRANS table, I will use SSQLFORM. INSERT DATA INTO THE TABLE The following has has the commands to insert four rows of data into the table. When you type them, be careful to include all the appropriate quotes and commas. And yes, include the incorrect spelling of Scottsdale. You will correct it in the next section. Note that Hippity Hopper has a null in place of his salary. This means that the salary is not available which is different from putting a salary of zero. With long commands, it is a better idea to press the F5 to make the text editing full-screen. You can type all of the lines before pressing F4. However, if there is an error on one of the lines, it will be more difficult to determine which line it is on. insert into pay values('AA','Everski','Willy',45000,'Scottsdale',0); (press F4) (Shift-PgUp,Del) insert into pay values('BB','Everski','Wilshe',60000,'Scootsdale',0); (press F4) (Shift-PgUp,Del) insert into pay values('CC','Hopper','Hippity',null,'Phoenix',0); (press F4) (Shift-PgUp,Del) insert into pay values('DD','Nosebleed','Harvey',20000,'Peoria',0); (press F4) (Shift-PgUp,Del) TUTORIAL-3 Although the above is SQL syntax, SSQL allows a much easier way to fill the tables with data. Let's add data to the TRANS table the easy way. Press ALT-Q to access the SQL menu. Press F to access the FORMS program which allows flexible data entry. Type TRANS.DBF for the file name. After you have entered all the data, press ESC to exit the FORMS program. 1 AA r4 3 3.45 2 AA r6 1 2.50 3 BB r4 5 6.78 If you made any mistakes, you should be able to correct them after going through the next section on updates. UPDATE DATA IN A TABLE You need to make some changes to the table. Scootsdale needs to be changed to Scottsdale update pay set city = 'Scottsdale' where city = 'Scootsdale'; (press F4) (Shift-PgUp,Del) The salary for everyone needs to be increased by 10%. update pay set salary = salary * 1.1; (press F4) (Shift-PgUp,Del) TUTORIAL-4 Let's do something a bit more complex. Total the sales (cost*qty) by Willy Everski ('AA') from the TRANS table and update the TOT_SOLD column in the pay table. To do that type the following: update pay set tot_sold = (select sum(cost*qty) from trans where sales_prsn = 'AA') where code = 'AA'; (press F4) (Shift-PgUp,Del) DELETE A ROW FROM A TABLE Harvey Nosebleed has been fired so you want to delete the row that contains the data for Harv. delete from pay where last='Nosebleed'; (press F4) (Shift-PgUp,Del) In a manner similar to the update, the where clause describes which row should be deleted. RETRIEVE DATA FROM A TABLE The select command is used to retrieve data from a table. The following select command retrieves all the data in the table. select * from pay; (press F4) CODE LAST FIRST SALARY CITY TOT_SOLD ---- --------------- --------------- ------ ------------ -------- AA Everski Willy 49500 Scottsdale 12.85 BB Everski Wilshe 66000 Scottsdale 0.00 CC Hopper Hippity Phoenix 0.00 The above is in a text window on the right of the screen. Notice that the screen is cut off at the salary amount. The best solution is to press F5 to make the text window full-screen. (Remember to press F5 again to shrink it). Otherwise you can move the cursor to the heading line and press the END key to scroll to the end of the line. TUTORIAL-5 Let's do two optional operations: Edit it. Add the heading "THE COMPLETE PAY TABLE" at the top of the window. Print it. Press ALT-F,P to print the contents of a text window. Now erase it. Press ALT-F3 to close the window. It will ask whether you want to save the changes. Press N. (press Shift-PgUp,Del) WHAT HAPPENS WHEN YOU FORGET THE NAMES OF THE COLUMNS Before we go any further, it may be useful to find out the names of the columns in a table. The struct command will do that for us. Type: struct pay; COLUMN DECIMAL NOT COLUMN NAME DATA TYPE WIDTH PLACES NULL UNIQUE INDEX CODE character 3 X X LAST character 15 X FIRST character 15 X SALARY numeric 5 0 CITY character 12 TOT_SOLD numeric 7 2 (press F4) (You won't be able to see all of it in the narrow window so press F5 to zoom the window). (press ALT-F3 to close the window) (Shift-PgUp,Del) The following shows how to retrieve the first name and last name for all the rows. select first, last from pay; (press F4) first last --------------- --------------- Willy Everski Wilshe Everski Hippity Hopper (press ALT-F3 to close the window) (press Shift-PgUp,Del) TUTORIAL-6 The following displays the rows of employees which have salaries of less than $58,000. Notice that the row for Hippity Hopper is not displayed because all nulls are excluded. select * from pay where salary < 58000; (press F4) last first salary city ------------- ------------- ------ ------------ Everski Willy 49500 Scottsdale (press ALT-F3 to close the window) (press Shift-PgUp,Del) ***************************************************************** * FROM NOW ON I WILL ASSUME THAT YOU KNOW ABOUT THE F4, ALT-F3, * * AND SHIFT-PGUP, DEL ***************************************************************** ELIMINATING DUPLICATE ROWS We can eliminate duplicate rows with the DISTINCT modifier. The TRANS table has three rows but two of them have duplicate product codes. We can display a list of all the DIFFERENT product codes with: select distinct prod from trans; prod ---- r4 r6 AGGREGATE FUNCTIONS (AVG, MIN, MAX,SUM,COUNT) These functions operate on the whole table so they cannot normally exist with simple column names. The SUM function adds items in a numeric column as in: select sum(salary) from pay; SUM(salary) ----------- 115500 TUTORIAL-7 The COUNT function simply counts the number of rows that have values. The ones that contain NULL are not counted. You can use a shortcut with the '*' to count all rows: select count(*) from pay; CNT(*) ------ 3 However when we count the number of rows with salary, only two are listed because Hippity Hopper doesn't have a salary. select count(salary) from pay; CNT(salary) ----------- 2 When you calculate the average salary, it will correctly divide by two, not three: select avg(salary) from pay; AVG(salary) ----------- 57750 CALCULATIONS You can do calculations but you have to be careful. It will take us three times to get it the way we want. Let's assume we want to display the qty, cost and the extended cost for each item. Type: select qty, cost, qty*cost from trans; qty cost qty --- ----- -------- 3 3.45 10 1 2.50 2 5 6.78 34 Hey! That's not right! 3 * 3.45 is not just 10, it is 10.35. Well, by putting qty first in the list of calculations, it based the calculation on the data type of qty which is a whole number so the decimal portion did not appear. TUTORIAL-8 Let's try it again. Type: select qty, cost, cost*qty from trans; qty cost cost --- ----- ---------- 3 3.45 10.35 1 2.50 2.50 5 6.78 33.90 That is better but we need a better heading. If you don't change the heading, it will be the first column name in the calculation. Let's change the heading to ExtCost: select qty, cost, cost*qty ExtCost from trans; qty cost ExtCost --- ----- ------------ 3 3.45 10.35 1 2.50 2.50 5 6.78 33.90 SORTING THE ROWS Let's print all the rows in the TRANS table but sort them by product code: select * from trans order by prod; TRANS_CODE SALES_PRSN PROD QTY COST ---------- ---------- ---- --- ----- 1 AA r4 3 3.45 3 BB r4 5 6.78 2 AA r6 1 2.50 GROUP INFORMATION Now for something a bit more advanced let's count how many sales EACH salesperson made. We can see above that AA made two sales and BB made one sale. We are going to group (re-arrange) the information by SALES_PRSN and count the number of rows based on each value in the group: select sales_prsn, count(sales_prsn) from trans group by sales_prsn; sales_prsn CNT(sales_prsn) ---------- --------------- AA 2 BB 1 TUTORIAL-9 THE JOIN The power of SQL is seen through the more advanced commands. The join allows us to merge tables. We need to specify a common column between the tables. In our example, the column CODE in the pay table describes the same information as SALES_PRSN in the trans table. Let's display the name of the salesperson along with the product code and the quantity sold. select first, last, prod, qty from pay, trans where code=sales_prsn; first last prod qty --------------- --------------- ---- --- Willy Everski r4 3 Willy Everski r6 1 Wilshe Everski r4 5 THE SUBQUERY The typical subquery starts processing at the last subquery and works its way back up. Let's display the names of all salespersons who have sold product which cost less than $5. The bottom query gathers the codes of persons who have sold products less than $5. That information is passed back to the top query which finds the names based on the codes. select first, last from pay where code in (select sales_prsn from trans where cost < 5); first last --------------- --------------- Willy Everski CREATE A VIEW A view is an alternate way of looking at a table or even a combination of tables. It is also known as a derived table because a view is derived from one or more base tables. We will create a view which excludes salary information. The view is based on a select statement. The view accesses data in the base table every time it is used in a select statement. There is never any data contained in the view. The following creates the view: create view pay1 as select code, last, first, city from pay; (press F4) TUTORIAL-10 Now let's see what happens when all the columns of the view are selected. select * from pay1; (press F4) CODE LAST FIRST CITY ---- --------------- --------------- ------------ AA Everski Willy Scottsdale BB Everski Wilshe Scottsdale CC Hopper Hippity Phoenix (press ALT-F3 to close the window) (press Shift-PgUp,Del) DROP A TABLE When a table is dropped, the description of the table is erased from the disk. The drop command will only work on an empty table. The delete command is needed to delete all the data in the table then the drop command erases the table from the disk. delete from pay; (press F4) (press Shift-PgUp,Del) drop table pay; (press F4) (press Shift-PgUp,Del) drop view pay1; (press F4) (press Shift-PgUp,Del) EXIT SSQL Press ALT-X to exit. When it asks you whether you want to save the untitled file, press N. TUTORIAL-11