Q141171: PRB: RDO Forward-Only Cursor Doesn’t Allow MoveLast

Article: Q141171
Product(s): Microsoft Visual Basic for Windows
Version(s): 4.00
Operating System(s): 
Keyword(s): kbenv kbDatabase kbODBC
Last Modified: 18-FEB-2000

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The information in this article applies to:

- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 
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SYMPTOMS
========

If you try to use the MoveLast method on a forward-only remote data object
recordset, you receive the error

  "S1106: [Microsoft][ODBC SQL Server Driver]Fetch type out of range".

Forward-only resultsets are the only type returned by the OpenResultset method.

CAUSE
=====

Forward-only cursors only allow the use of MoveNext methods. This is a
limitation of ODBC.

RESOLUTION
==========

There is no direct way to implement an exact copy of MoveLast with code when
using a resultset with a forward-only cursor. The following code loops through
and touches all records in a resultset. When the loop finishes, the current
record will be the EOF marker.

     'The following code loops through all the records in a resultset
     While Not rdoToMove.EOF

        'do any processing here
        rdoToMove.MoveNext
     Wend

To determine the number of records in a resultset, code a loop like the one above
and increment a count variable inside the loop.

STATUS
======

This behavior is by design.

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

When RDO works with a forward-only resultset, it uses a call to the ODBC API
function SQLExtendedFetch to obtain data. As one of its parameters, this
function takes a value that specifies the type of fetch to be performed. ODBC
specifies that when a resultset has a forward-only cursor, this fetch argument
may only be SQL_FETCH_NEXT. If the argument is something besides this constant,
ODBC returns 'S1106: Fetch type out of range,' indicating that the argument was
invalid. For more information, see the reference listed in the References
section below.

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

1. Start Visual Basic.

2. On the File menu, click New Project.

3. Double-click the Command button icon in the Toolbox to create a command
  button on the form.

4. Insert the following code in the command button's Click event. Replace
  strDSN, strConnect, and strSQL with the relevant values for your database.

     Private Sub Command1_Click()
               Dim ps As rdoPreparedStatement
               Dim conn As rdoConnection
               Dim strDSN As String
               Dim strConnect As String
               Dim strSQL As String

               strDSN = "pubs"
               strConnect = "uid=sa;pwd=;database=pubs"
               strSQL = "Select * From Authors"

               With rdoEnvironments(0)
                   .CursorDriver = rdUseOdbc
               Set conn = .OpenConnection _
                 (strDSN, rdDriverNoPrompt, False, strConnect)
               End With
               Set ps = conn.CreatePreparedStatement("", strSQL)
               Set rs = ps.OpenResultset(rdOpenForwardOnly)

               rs.MoveLast      'this line causes the error

     End Sub

5. On the Run menu, click Start (ALT, R, S) or press the F5 key. The program
  will stop when it reaches the rs.Movelast line, and give the error listed
  above.

REFERENCES
==========

Microsoft ODBC 2.0 Programmer's Reference and SDK Guide: SQLExtendedFetch
function - return code S1106.

Additional query words: 4.00 vb4win vb432

======================================================================
Keywords          : kbenv kbDatabase kbODBC 
Technology        : kbVBSearch kbAudDeveloper kbVB400Search kbVB400
Version           : 4.00
Issue type        : kbprb

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