Microsoft KB Archive/139759

= FIX: CDatabase::ExecuteSQL Fails with UNICODE Build =

Article ID: 139759

Article Last Modified on 11/21/2006

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APPLIES TO


 * Microsoft Foundation Class Library 4.2, when used with:
 * Microsoft Visual C++ 4.0 Standard Edition

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This article was previously published under Q139759



SYMPTOMS
Trying to run a program that contains a call to CDatabase::ExecuteSQL that has been built for UNICODE results in a CDBException being thrown with an error message from the ODBC driver. The message depends on the SQL Statement and the ODBC driver. For example, trying to execute an INSERT statement on a data source that uses the Microsoft Access ODBC driver results in the following error message:

  Invalid SQL statement; expected 'DELETE', 'INSERT', 'PROCEDURE', 'SELECT', or 'UPDATE'. State:37000,Native:-3500,Origin: [Microsoft][ODBC Microsoft Access 7.0 Driver]



CAUSE
The SQL string passed to CDatabase::ExecuteSQL is a UNICODE string, and the ODBC API expects all arguments that are strings to be ASCII strings.



RESOLUTION
To work around this bug, you have to convert the string yourself, and then cast the resultant ASCII string to an LPCTSTR when you pass it to CDatabase::ExecuteSQL. The cast is necessary because CDatabase::ExecuteSQL expects a wide character string.

For example, using the following code to delete all the records in a table will fail in an MFC 4.0 program:

CString  strSQL = _T("DELETE FROM Table1"); MyDatabase.ExecuteSQL(strSQL); To make the code work, you need to use code similar to this code: #include  // add this include for WideCharToMultiByte .  .   .   CString   strSQL = _T("DELETE FROM Table1"); char*    szAscii = new char[strSQL.GetLength + 1];

WideCharToMultiByte(CP_ACP,0,strSQL,-1,    szAscii,strSQL.GetLength + 1,NULL,NULL); MyDatabase.ExecuteSQL((LPCTSTR)szAscii); delete [] szAscii;



STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug was corrected in Visual C++ 4.1.



MORE INFORMATION
In general, you can use the MFC ODBC classes in UNICODE programs. The MFC ODBC classes will handle the UNICODE/ASCII conversions for ODBC API calls. CDatabase::ExecuteSQL is missing this conversion support.

Additional query words: kbVC400bug

Keywords: kbbug kbdatabase kbfix kbvc410fix KB139759

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