DOCUMENT:Q148917  03-AUG-2001  [visualc]
TITLE   :How to Use the DAO Dynaset with Microsoft SQL Server 6.0
PRODUCT :Microsoft C Compiler
PROD/VER:4.00
OPER/SYS:
KEYWORDS:kbDAOsearch kbDatabase kbMFC kbVC

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - The Microsoft Foundation Classes (MFC), included with:
    - Microsoft Visual C++, 32-bit Editions, version 4.0 
-------------------------------------------------------------------------------

SUMMARY
=======

You can use CDaoRecordset to insert, update, or delete records in a table in a
Microsoft SQL Server 6.0 database. There are two ways to do it:

 - Use a direct ODBC connection in CDaoDatabase::Open(). In this case, there
   must be a unique index on one of the fields in the recordset. If there is no
   such index, the recordset will become read only.

-or-

 - Use a linked table through a Microsoft Access 7.0 database. You must have a
   unique index on one of the fields in the recordset. Microsoft Access asks for
   a unique identifier while creating the linked table if the table does not
   have a unique index. If you do not specify a field as the unique identifier
   and there is no unique index, the recordset will become read only.

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

Using a Direct ODBC Connection in CDaoDatabase::Open()
------------------------------------------------------

If you create a DAO dynaset without specifying a unique index on one or more
fields in the recordset and then try updating or adding a record, MFC DAO will
throw an exception and you will see the following errors in the MFC Trace
output:

AddNew fails with this message:

   

   DAO Call Failed.
   m_pDAORecordset->AddNew()
   In file daocore.cpp on line 4498
   scode = 800A0BD3

   Error Code = 3027
   Source = DAO.Recordset
   Description = Can't update. Database or object is read-only.

Edit() fails with a similar message:

   

   DAO Call Failed.
   m_pDAORecordset->Edit()
   In file daocore.cpp on line 4525
   scode = 800A0BD3

   Error Code = 3027
   Source = DAO.Recordset
   Description = Can't update. Database or object is read-only.

Using a Linked Table Through a Microsoft Access 7 Database
----------------------------------------------------------

If you create a DAO dynaset on a linked table in Microsoft Access, the recordset
becomes read only if there is no unique identifier specified in Microsoft Access
and there is no unique index on some field(s) in the recordset. You will see the
same error messages from AddNew or Edit as shown in the previous case.

One way to satisfy the requirement for a unique index is to create an index on
the primary key. Note that if you use the PRIMARY KEY specification new to SQL
Server version 6.0 when creating your tables, you will automatically generate a
unique index on the primary key. This syntax is demonstrated here:

   CREATE TABLE MyTable
          (column1 CHAR(10) PRIMARY KEY NOT NULL,
           column2 CHAR(10))

Additional query words: kbinf 4.00

======================================================================
Keywords          : kbDAOsearch kbDatabase kbMFC kbVC 
Technology        : kbAudDeveloper kbMFC
Version           : 4.00

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2001.