Q186138: HOWTO: Wrap Remote Views into One SQL Transaction

Article: Q186138
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0,3.0b,5.0,5.0a
Operating System(s): 
Keyword(s): 
Last Modified: 13-AUG-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a 
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SUMMARY
=======

You can wrap multiple remote views into one transaction, which allows you to
commit or rollback all changes to the back-end data tables in one step. For
example, a bank transfer between a savings account and a checking account. If
the subtraction from the savings account fails because of insufficient funds,
you do not want the addition to the checking account to be completed. Thus, you
can rollback the entire bank transaction.

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

In order to wrap the views into a transaction you must use Shared Connections
and set the Transaction property of SQLSetProp to Manual (2).

When these two settings are set, SQLCommit() or SQLRollback() may be used to
commit or rollback the transactions. The following steps show how to wrap two
separate remote views in a transaction.

Step-by-Step Example
--------------------

1. Create a connection to your back end data and name it Myconnection.

2. Create two updateable remote views named Myview1 and Myview2.

3. Make the views share the connection by modifying the remote view. From the
  Query menu choose Advanced Options. This displays a dialog box that contains
  the Shared Connection check box. Select the check box and click OK.

4. In the Command window or in code issue the following commands:

        USE Myview1
        USE Myview2 in 0
        m.Handle = CursorGetProp('ConnectHandle','Myview1')
        =SQLSETPROP(m.Handle,'Transaction',2)

  This code gets the connection handle from the cursor and sets the Transaction
  property to two (2), which is manual mode. This mode allows you to use the
  SQLCOMMIT or SQLROLLBACK functions.

5. Modify some data in the views and issue the following code:

        =Tableupdate(1,.t.,'Myview1')
        =Tableupdate(1,.t.,'Myview2')
        =SQLCommit(m.Handle)
        =Requery('Myview1')
        =Requery('Myview2')

  You can replace the SQLCommit with SQLRollback and see the data go back to its
  original value.

REFERENCES
==========

For more information on creating connections:

  Visual FoxPro Developer's Guide, Chapter 8, "Defining a Connection";
  "Creating Views"

For more information about making an updateable view:

  Visual FoxPro Online Help; search on "View Designer"; topic: "Update Tab"

(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by David
Botzenhart, Microsoft Corporation


Additional query words: kbDSupport kbDSE kbnokeyword

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b kbVFP500 kbVFP500a
Version           : WINDOWS:3.0,3.0b,5.0,5.0a
Issue type        : kbhowto

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