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Q230491: PRB: CDBVariant Contains Wrong BOOL Value with GetFieldValue

Article: Q230491
Product(s): Microsoft C Compiler
Version(s): winnt:6.0
Operating System(s): 
Keyword(s): kbDatabase kbMFC kbODBC kbVC kbVC600 kbGrpDSVCDB
Last Modified: 07-MAY-2001

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The information in this article applies to:

- 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
========

When calling the CRecordset::GetFieldValue() method that accepts a CDBVariant
object as a parameter and the target field in the database is a bit field, the
BOOL value (m_boolVal) is incorrect.

RESOLUTION
==========

Use an explicit type other then SQL_C_BIT, such as SQL_C_UTINYINT or
SQL_C_SLONG, as the type of variable to bind to.

Please see the More Information for details.

STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products listed at
the beginning of this article.

MORE INFORMATION
================

The following steps use the SQL Server Pubs database as an example:

Steps to Reproduce Behavior
---------------------------

1. Create an MFC Single Document Interface project with database header file
  support.

2. Create a menu item or button event handler.

3. Type the following code in the handler and change the connect string to
  reflect your SQL Server database:

  	CDatabase db;
  	db.OpenEx(_T("Driver=SQL Server;Server=(local);Database=Pubs;UID=sa;PWD=;"));

  	CRecordset rs;
  	rs.m_pDatabase = &db;
  	rs.Open(CRecordset::forwardOnly, _T("SELECT * FROM authors"));

  	CDBVariant varField;
  	rs.GetFieldValue(_T("contract"),varField);
  	BOOL boolValue = varField.m_boolVal;

4. Observe the value of boolValue. It will be incorrect.

Workaround
----------

Use SQL_C_UTINYINT or SQL_C_SLONG explicitly in the CRecordset::GetFieldValue()
method. Replace the last two lines of the previous code block with one of the
following:

  	rs.GetFieldValue(_T("contract"),varField,SQL_C_UTINYINT);
  	BYTE byteValue = varField.m_chVal;

-or-

  	rs.GetFieldValue(_T("contract"),varField,SQL_C_SLONG);
  	BOOL boolValue = varField.m_boolVal;

Additional query words: boolean odbc

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Keywords          : kbDatabase kbMFC kbODBC kbVC kbVC600 kbGrpDSVCDB 
Technology        : kbVCsearch kbAudDeveloper kbVC600 kbVC32bitSearch
Version           : winnt:6.0
Issue type        : kbprb

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