Tricks of the Windows Gam…ming Gurus (2nd Edition)/Disc2.iso/msdn_vcb/samples/vc98/mfc/database/daotable/querydef.cpp

C/C++ Source or Header | 1998-03-27 | 11.7 KB | 440 lines

// querydef.cpp : MFC DAO QueryDef specific functions
//
// contains all querydef specific functions:
//
// This is a part of the Microsoft Foundation Classes C++ library.
// Copyright (C) 1992-1998 Microsoft Corporation
// All rights reserved.
//
// This source code is only intended as a supplement to the
// Microsoft Foundation Classes Reference and related
// electronic documentation provided with the library.
// See these sources for detailed information regarding the
// Microsoft Foundation Classes product.

#include "stdafx.h"
#include "querydef.h"

// check for duplicate query name in querydef collection
// of database object
// IN: pDatabase--pointer to database whose querydef collection we will access
// IN: strQueryName--the name of the querydef we want to check for existence
// RETURN: TRUE if the specified querydef already exists, FALSE otherwise
BOOL IsExistentQuery(CDaoDatabase *pDatabase, CString strQueryName)
{
    // if no database, then done immediately
    if (pDatabase == NULL)
        return FALSE;

    // initialize status indicator
    BOOL bDuplicateQueryName = TRUE;

    // see if there is a query by this name already--duplicate
    // named querys are not accepted
    CDaoQueryDefInfo queryInfo; // only needed for the call

    // MFC exception handler macros used
    TRY
    {
        // this call will throw an exception if there is no
        // query by the specified name--test for duplication
        pDatabase->GetQueryDefInfo(strQueryName, queryInfo);
    }
    CATCH (CDaoException, e)
    {
        // if this is an 'Item not found' exception, we are
        // cleared to create the query -- else this is
        // a duplicate queryname and we got another exception
        // which is irrelevant for our purposes
        if (e->m_pErrorInfo->m_lErrorCode == 3265)
            bDuplicateQueryName = FALSE;
    }
    AND_CATCH (CMemoryException, e)
    {
        // do nothing
        ;
    }
    END_CATCH

    return bDuplicateQueryName;
}

// wraps the CreateQueryDef call with an exception handler and duplicate
// name check
// IN: pDatabase--pointer to database whose querydef collection we will access
// OUT: ppQueryDef--pointer to pointer of querydef we will create and return
// RETURN: TRUE if creation succeeded, FALSE otherwise
BOOL createNewQueryDef(CDaoDatabase * pDatabase,
                                    CDaoQueryDef **ppQueryDef,
                                    CString strQueryName)
{
    // if no database, then done immediately
    if (pDatabase == NULL)
        return FALSE;

    // check for existing query with this name just to be safe
    if (IsExistentQuery(pDatabase, strQueryName))
    {
        AfxMessageBox(_T("A query by that name already exists."));

        // return FALSE since can't create duplicate query
        return FALSE;
    }

    // initialize creation failure indicator
    BOOL bCreateFailed = FALSE;

    // cleanup any existing querydef
    if (*ppQueryDef != NULL)
        delete *ppQueryDef;

    // construct querydef
    *ppQueryDef = new CDaoQueryDef(pDatabase);

    // failed to allocate so exit with failure
    if ((*ppQueryDef) == NULL)
        return FALSE;

    // no duplication, so create the querydef if possible
    TRY
    {
        (*ppQueryDef)->Create(strQueryName);
    }
    CATCH (CDaoException, e)
    {
        // construct a meaningful message
        CString strMessage = _T("Couldn't create querydef--Exception: ");
        strMessage += e->m_pErrorInfo->m_strDescription;

        AfxMessageBox(strMessage);

        // indicate failure
        bCreateFailed = TRUE;

        // delete the querydef on failure
        if (*ppQueryDef != NULL)
        {
            delete *ppQueryDef;
            *ppQueryDef = NULL;
        }
    }
    AND_CATCH (CMemoryException, e)
    {
        // output status
        AfxMessageBox(_T("Failed to create querydef--Memory exception thrown."));

        // indicate failure
        bCreateFailed = TRUE;

        // delete the querydef on failure
        if (*ppQueryDef != NULL)
        {
            delete *ppQueryDef;
            *ppQueryDef = NULL;
        }
    }
    END_CATCH

    // return TRUE if creation succeeds
    return (!bCreateFailed);
}

// wraps the OpenQueryDef call with an exception handler
// IN: pDatabase--pointer to database whose querydef collection we will access
// OUT: ppQueryDef--pointer to pointer to querydef we will open and return
// IN: strQueryName--the name of the querydef we want to check for existence
// RETURN: TRUE if the open succeeded, FALSE otherwise
BOOL openQueryDef(CDaoDatabase * pDatabase, CDaoQueryDef **ppQueryDef,
                  CString strQueryName)
{
    // if no database, then done immediately
    if (pDatabase == NULL)
        return FALSE;

    // initialize creation failure indicator
    BOOL bOpenFailed = FALSE;

    // cleanup any existing querydef
    if (*ppQueryDef != NULL)
        delete *ppQueryDef;

    // construct querydef
    *ppQueryDef = new CDaoQueryDef(pDatabase);

    // failed to allocate so exit with failure
    if ((*ppQueryDef) == NULL)
        return FALSE;

    // open the querydef if possible
    TRY
    {
        (*ppQueryDef)->Open(strQueryName);
    }
    CATCH (CDaoException, e)
    {
        // construct a meaningful message
        CString strMessage = _T("Couldn't open querydef--Exception: ");
        strMessage += e->m_pErrorInfo->m_strDescription;

        AfxMessageBox(strMessage);

        // indicate failure
        bOpenFailed = TRUE;

        // delete the querydef on failure
        if (*ppQueryDef != NULL)
        {
            delete *ppQueryDef;
            *ppQueryDef = NULL;
        }
    }
    AND_CATCH (CMemoryException, e)
    {
        // output status
        AfxMessageBox(_T("Failed to open querydef--Memory exception thrown."));

        // indicate failure
        bOpenFailed = TRUE;

        // delete the querydef on failure
        if (*ppQueryDef != NULL)
        {
            delete *ppQueryDef;
            *ppQueryDef = NULL;
        }
    }
    END_CATCH

    // return TRUE if open succeeds
    return (!bOpenFailed);
}

// append the specified query def to the collection of querydefs in the
// database object
//
// IN: pDatabase--pointer to database whose querydef collection we will access
// IN: pQueryDef--pointer to querydef we will append to the collection
// RETURN: TRUE if querydef appended, FALSE otherwise
BOOL appendQueryDef(CDaoDatabase *pDatabase, CDaoQueryDef *pQueryDef)
{
    // if no database, then done immediately
    if (pDatabase == NULL)
        return FALSE;

    // initialize success indicator
    BOOL bSuccess = TRUE;

    // append the querydef to the collection
    // catch exceptions using C++ style exceptions
    TRY
    {
        pQueryDef->Append();
    }
    CATCH (CDaoException, e)
    {
        // construct informative message
        CString strMessage = _T("Couldn't append QueryDef--Exception: ");
        strMessage += e->m_pErrorInfo->m_strDescription;

        // output status
        AfxMessageBox(strMessage);

        // failure
        bSuccess = FALSE;
    }
    AND_CATCH (CMemoryException, e)
    {
        // output status
        AfxMessageBox(_T("Failed to append querydef--Memory exception thrown."));

        // failure
        bSuccess = FALSE;
    }
    END_CATCH

    // return status
    return bSuccess;
}

// fill a querydef info struct--handle exceptions
// IN: pDatabase--pointer to database whose querydef collection we will access
// IN/OUT: pQueryInfo--pointer to querydef info struct we want to fill in
// IN: index--index into the collection of querydefs for the item we want
//     pass a negative value if you want to use the name in pQueryInfo
//     to look up the querydef
// IN: bReportErrors--if TRUE, report any errors that occur, else silent
//     TRUE by default
// RETURN: TRUE if information obtained, FALSE otherwise
BOOL getQueryInfo(CDaoDatabase *pDatabase, CDaoQueryDefInfo *pQueryInfo,
                  int index, BOOL bReportErrors /*= TRUE*/)
{
    // if the database is non-existent, then the answer is obvious
    if (pDatabase == NULL)
        return FALSE;

    // initialize success indicator
    BOOL bSuccess = TRUE;

    TRY
    {
        // try to get info on the querydef either by index or by name
        if (index < 0)
            pDatabase->GetQueryDefInfo(pQueryInfo->m_strName, *pQueryInfo,
                                AFX_DAO_ALL_INFO );
        else
            pDatabase->GetQueryDefInfo(index, *pQueryInfo,
                                AFX_DAO_ALL_INFO );

    }
    CATCH (CDaoException, e)
    {
        // construct a meaningful message if requested
        if (bReportErrors)
        {
            CString strMessage = _T("Couldn't get information on QueryDef--Exception: ");
            strMessage += e->m_pErrorInfo->m_strDescription;

            AfxMessageBox(strMessage);
        }

        // indicate failure
        bSuccess = FALSE;
    }
    AND_CATCH (CMemoryException, e)
    {
        // output status if requested
        if (bReportErrors)
            AfxMessageBox(_T("Failed to get info on QueryDef--Memory exception thrown."));

        // indicate failure
        bSuccess = FALSE;
    }
    END_CATCH

    // return status
    return bSuccess;
}

// wrap query deletion with exception handlers
// check for duplicate query name in query collection
// of tabledef object
// IN: pDatabase--pointer to database whose querydef collection we will access
// IN: strQueryName--the name of the querydef we want to delete
// RETURN: TRUE if the querydef was deleted, FALSE otherwise
BOOL deleteQuery(CDaoDatabase *pDatabase, CString strQueryName)
{
    // if the database is non-existent, then the answer is obvious
    if (pDatabase == NULL)
        return FALSE;

    // initialize success indicator
    BOOL bSuccess = TRUE;

    // MFC exception handler macros used
    TRY
    {
        pDatabase->DeleteQueryDef(strQueryName);
    }
    CATCH (CDaoException, e)
    {
        CString strMessage = _T("Couldn't delete the query--Exception: ");
        strMessage += e->m_pErrorInfo->m_strDescription;

        AfxMessageBox(strMessage);

        // indicate failure
        bSuccess = FALSE;
    }
    AND_CATCH (CMemoryException, e)
    {
        AfxMessageBox(_T("Failed to delete the query--Memory exception thrown."));

        // indicate failure
        bSuccess = FALSE;
    }
    END_CATCH

    return bSuccess;
}

// create a querydef and set its properties, append it to
// the collection
// IN: pDatabase--pointer to database whose querydef collection we will access
// IN/OUT: ppQueryDef--pointer to pointer of querydef we will process
// IN: pQI--pointer to information needed to create the querydef
// RETURN: TRUE if all processing succeeds, FALSE otherwise
BOOL createSetAndSaveNewQueryDef (CDaoDatabase * pDatabase,
                                    CDaoQueryDef **ppQueryDef,
                                    CDaoQueryDefInfo *pQI)
{
    // if no database, then done immediately
    if (pDatabase == NULL)
        return FALSE;

    // initialize failure indicator
    BOOL bFailure = TRUE;

    // call our create function and continue if it succeeds
    if (createNewQueryDef(pDatabase, ppQueryDef, pQI->m_strName))
    {
        // can only specify some properties on create, so specify the rest now
        if (modifyQueryDef (pDatabase, *ppQueryDef, pQI))
        {
            // now store the query def permanently
            if (appendQueryDef(pDatabase, *ppQueryDef))
            {
                // if you get here, you've succeeded,
                bFailure = FALSE;
            }
        }
    }

    // return TRUE if everything succeeds
    return (!bFailure);
}

// set the properties of the query def after it has been appended
//
// IN: pDatabase--pointer to database whose querydef collection we will access
// IN: pQueryDef--pointer to  querydef we will modify
// IN: pQI--pointer to information needed to modifiy the querydef
// RETURN: TRUE is modification succeeds, FALSE otherwise
BOOL modifyQueryDef (CDaoDatabase * pDatabase,
                     CDaoQueryDef *pQueryDef,
                     CDaoQueryDefInfo *pQI)
{
    // if no database, then done immediately
    if (pDatabase == NULL)
        return FALSE;

    // initialize success indicator
    BOOL bSuccess = TRUE;

    // MFC exception handler macros used
    TRY
    {
        pQueryDef->SetSQL(pQI->m_strSQL);
        pQueryDef->SetName(pQI->m_strName);
    }
    CATCH (CDaoException, e)
    {
        CString strMessage = _T("Couldn't modify the query--Exception: ");
        strMessage += e->m_pErrorInfo->m_strDescription;

        AfxMessageBox(strMessage);

        // indicate failure
        bSuccess = FALSE;
    }
    AND_CATCH (CMemoryException, e)
    {
        AfxMessageBox(_T("Failed to modify the query--Memory exception thrown."));

        // indicate failure
        bSuccess = FALSE;
    }
    END_CATCH

    return (bSuccess);
}