Using Microsoft Access As a DDE Server

Microsoft Access DDE as both a destination (client) application and a source (server) application. Although Microsoft Access doesn't support automatic linking, it manually updates linked data at specified intervals. The client application is notified when a change has occurred in a Microsoft Access database. The client application can then update the linked data. In most cases, this update occurs as fast as an automatic update. You can specify the interval between DDE link updates by setting the Refresh Interval option under the Multiuser/ODBC category in the Options dialog box (View menu). In the same dialog box under the General category, Enable DDE Refresh turns this feature on or off, and Ignore DDE Requests instructs Microsoft Access to ignore or accept DDE requests from other applications.

Each DDE conversation is established on a particular topic, usually a data file, with the conversation thereafter limited to the items associated with that topic. For example, if you are running Word for Windows and want to insert data from a particular Microsoft Access database into a Word for Windows document, you need to initiate a DDE conversation with Microsoft Access by opening a channel and specifying the database name as the topic. You can then use that channel to obtain data from the database.

The following example shows how to create a Word for Windows WordBasic macro that uses Microsoft Access as a DDE server. (For this example to work, Microsoft Access must either be running or be listed in the path command in your AUTOEXEC.BAT file.)

Sub MAIN
    ' Using the System topic, open the NWIND.MDB database.
    ' The database must be open before you can use other DDE topics.
    Chan1 = DDEInitiate("MSAccess", "System")
    DDEExecute Chan1, "[OpenDatabase C:\ACCESS\NWIND.MDB]"

    ' Get all the data from the Orders and Products query.
    Chan2 = DDEInitiate("MSAccess", "NWIND;QUERY Orders and Products")
    MyData$ = DDERequest$(Chan2, "All")
    DDETerminate Chan2

    ' Close the database.
    DDEExecute Chan1, "[CloseDatabase]"
    DDETerminate Chan1

    ' Insert the data into a text file.
    Open "MYDATA.TXT" For Append As #1
    Print #1, MyData$
    Close #1
End Sub

As a DDE server, Microsoft Access supports the following topics:

The System topic

The name of a database

The name of a table

The name of a query

A Microsoft Access SQL statement

The System Topic

The System topic is a standard topic for all Windows-based applications. It returns information about the topics supported by the application.

The System topic supports the following Microsoft Access items.

The database Topic

The database topic is the filename of an existing Microsoft Access database. You can specify just the base name, as in the NWIND database, or its full path and .MDB extension, as in C:\ACCESS\NWIND.MDB. After you initiate a DDE conversation with the database, you can request a list of the objects in that database.

The database topic supports the following items.

The TABLE tablename, QUERY queryname, and SQL sqlstring Topics

These topics use the following syntax:

databasename;TABLE tablename

databasename;QUERY queryname

databasename;SQL [sqlstring]

The following table lists the valid items for the TABLE tablename, QUERY queryname, and SQL sqlstring topics.