Q129925: Requery Method Not Available on PassThrough Queries

Article: Q129925
Product(s): Microsoft Visual Basic for Windows
Version(s): 4.00
Operating System(s): 
Keyword(s): kbDatabase kbODBC
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition, 16-bit, for Windows, version 4.0 
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 
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SUMMARY
=======

Visual Basic version 4.0 adds the Requery method for the RecordSet object. This
method updates the data in a Recordset object by re-executing the query on which
the object is based. When you use Requery, all changes made to the data in the
underlying table by other users are displayed in the Recordset, and the first
record in the Recordset becomes the current record. This method is not available
for RecordSets created using the OpenRecordset method with the dbSQLPassthrough
option.

CAUSE
=====

The Requery method requires that column IDs are maintained and that column
datatypes and names are the same. For passthrough queries Visual Basic passes
the query through to the ODBC database without parsing it and has no way of
knowing that these values will be maintained, so it disallows requery. The same
is true for Crosstab queries without fixed column lists.

STATUS
======

This behavior is by design.

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

You can test whether or not your RecordSet can be Requeried by checking the
Restartable property of your RecordSet. The Restartable property returns a value
that indicates whether a Recordset object supports the Requery method.

Steps to Reproduce Behavior in Visual Basic Version 4.0
-------------------------------------------------------

You will need an ODBC datasource to query against. This example assumes a DSN
called "Pubs" exists with table named "Authors".

1. Start a new project in Visual Basic. Form1 is created by default.

2. Add the following code to the Form1_Click procedure.

     Sub Form_Click()
        Dim MyDB As Database, MyData As Recordset
        Set MyDB = DBEngine.Workspaces(0).OpenDatabase("", False, False, _
           "ODBC;DSN=pubs;uid=sa;pwd=")
        Set MyData = MyDB.OpenRecordset("Select * From authors",_
           dbOpenDynaset, dbSQLPassThrough)
        'other code here
        If MyData.Restartable = True Then '<== This will always be false.
           MsgBox "This RecordSet will be Requeried."
           MyData.Requery
        Else
           MsgBox "This RecordSet will not be Requeried."
           MyData.Close
        End If
        MyDB.Close
     End Sub

3. Start the program by choosing Run Start (or press the F5 key).

The MyData.Restartable property will always be False, since the sample uses
ExecuteSQL.

Additional query words: 4.00 vb4win vb4all

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Keywords          : kbDatabase kbODBC 
Technology        : kbVBSearch kbAudDeveloper kbVB400Search kbVB400 kbVB16bitSearch
Version           : 4.00

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