Q155848: PRB: ODBC Error When Using CRecordset Without Deriving From It

Article: Q155848
Product(s): Microsoft C Compiler
Version(s): 4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbProgramming kbusage kbdocfix kbDatabase kbMFC kbODBC kbVC kbGrpDSVCDB kbGrpDSMDAC kbD
Last Modified: 04-AUG-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
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SYMPTOMS
========

With Visual C++ 4.2 and later, you can use the CRecordset class without deriving
from it, allowing you to open a read-only recordset on any data source. This may
be helpful if you are using CRecordset::GetFieldValue(), for example. However,
when calling Open() for the CRecordset object, you may see a message box with
the following message in it:

  No columns were bound prior to calling SQLExtendedFetch

CAUSE
=====

The CDatabase object used by the CRecordset object loaded the ODBC cursor
library. The cursor library requires that there be at least one bound column for
a recordset. The Visual C++ documentation doesn't make this requirement clear.

RESOLUTION
==========

Do not load the cursor library by specifying FALSE for the last argument of
CDatabase::Open(). For example:

      CDatabase db;
      db.Open("MyDataSource", FALSE, FALSE, "ODBC;", FALSE);
      CRecordset rs( &db );
      rs.Open(...);
      ...

If your driver does not support dynasets, then the cursor library is required and
you will not be able to use the CRecordset class without deriving from it.

STATUS
======

Microsoft has confirmed this to be a problem with the Visual C++ 4.2
documentation. The Visual C++ 5.0 documentation has been changed to reflect this
information and states:

  Note if you declare a recordset object without deriving from CRecordset, do
  not have the ODBC Cursor Library loaded. The cursor library requires that the
  recordset have at least one bound column; however, when you use CRecordset
  directly, none of the columns are bound. The member functions
  CDatabase::OpenEx and CDatabase::Open control whether the cursor library will
  be loaded."

Additional query words:

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Keywords          : kbProgramming kbusage kbdocfix kbDatabase kbMFC kbODBC kbVC kbGrpDSVCDB kbGrpDSMDAC kbDSupport kbMDACNoSweep 
Technology        : kbAudDeveloper kbMFC
Version           : :4.2,5.0,6.0
Issue type        : kbprb

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