ACC: Procedure to Create Data Sources and Relink ODBC Tables

MORE INFORMATION

When you link a table to a Microsoft Access database using an ODBC Data Source, the information regarding that connection is stored in the Description property of the table. If you move the database to another computer that does not contain the Data Source Name (DSN) for the ODBC connection to the linked table, you receive the following error when you try to open the table: Visual Basic for Applications supports the RegisterDatabase method to create or modify the DSNs on a computer. Use it to refresh your existing ODBC connections with new information or create new TableDef objects based on the DSN.

When you implement this technique in your database, you ensure that a code mechanism exists that will set up and relink to any ODBC Data Sources that you use in your application.

The steps in the following example create a DSN for a SQL Server database:

1. Create a new database called TestODBC.mdb.
2. Create the following table to store SQL Server ODBC Data Source information. You can modify the fields in this table to store the DSN information for any ODBC driver. For many ODBC connections, the Server and Database entries will not be necessary because these values are saved with the DSN.

         Table: tblODBCDataSources
         -------------------------
         Field Name: DataBase
            Data Type: Text
            Field Size: 50
         Field Name: UID
            Data Type: Text
            Field Size: 50
         Field Name: PWD
            Data Type: Text
            Field Size: 50
         Field Name: Server
            Data Type: Text
            Field Size: 50
         Field Name: ODBCTableName
            Data Type: Text
            Field Size: 50
         Field Name: LocalTableName
            Data Type: Text
            Field Size: 50
         Field Name: DSN
            Data Type: Text
            Field Size: 50
   
         Table Properties: tblODBCDataSources
         ------------------------------------
         PrimaryKey: LocalTableName
   					

3. Create a record in the tblODBCDataSources table with information about your ODBC databases. This example uses a SQL Server connection to the Authors table in the Pubs database; substitute the correct information for your environment, and add a record for each linked table in your database:

         Field Name          Value
         -------------------------------------
         DataBase            Pubs
         UID                 <username>
         PWD                 <strong password>
         Server              SQLPUBS
         ODBCTableName       dbo.authors
         LocalTableName      Authors
         DSN                 Pubs
   						

   Note that the ODBCTableName represents the name of the table in the source database (in this example, SQL Server), and that the LocalTableName represents the name assigned to the linked table in the Access database.
4. Create a module and type or paste the following code. If you are not using all the connection-related parameters--for example, if you are not using the Server and Database arguments--comment out or omit the corresponding lines in the strConn definition. Otherwise, passing the arguments with empty values may cause your connection to fail.

         '***************************************************************
         'The DoesTblExist function validates the existence of a TableDef
         'object in the current database. The result determines if an
         'object should be appended or its Connect property refreshed.
         '***************************************************************
   
         Function DoesTblExist(strTblName As String) As Boolean
            On Error Resume Next
            Dim db As Database, tbl As TableDef
            Set db = CurrentDb
            Set tbl = db.TableDefs(strTblName)
            If Err.Number = 3265 Then   ' Item not found.
               DoesTblExist = False
               Exit Function
            End If
            DoesTblExist = True
         End Function
   
         Function CreateODBCLinkedTables() As Boolean
            On Error GoTo CreateODBCLinkedTables_Err
            Dim strTblName As String, strConn As String
            Dim db As Database, rs As Recordset, tbl As TableDef
            ' ---------------------------------------------
            ' Register ODBC database(s)
            ' ---------------------------------------------
            Set db = CurrentDb
            Set rs = db.OpenRecordset("tblODBCDataSources")
            With rs
               While Not .EOF
                  DBEngine.RegisterDatabase rs("DSN"), _
                           "SQL Server", _
                           True, _
                           "Description=VSS - " & rs("DataBase") & _
                           Chr(13) & "Server=" & rs("Server") & _
                           Chr(13) & "Database=" & rs("DataBase")
                  ' ---------------------------------------------
                  ' Link table
                  ' ---------------------------------------------
                  strTblName = rs("LocalTableName")
                  strConn = "ODBC;"
                  strConn = strConn & "DSN=" & rs("DSN") & ";"
                  strConn = strConn & "APP=Microsoft Access;"
                  strConn = strConn & "DATABASE=" & rs("DataBase") & ";"
                  strConn = strConn & "UID=" & rs("UID") & ";"
                  strConn = strConn & "PWD=" & rs("PWD") & ";"
                  strConn = strConn & "TABLE=" & rs("ODBCTableName")
                  If (DoesTblExist(strTblName) = False) Then
                     Set tbl = db.CreateTableDef(strTblName, _
                                   dbAttachSavePWD, rs("ODBCTableName"), _
                                   strConn)
                     db.TableDefs.Append tbl
                  Else
                     Set tbl = db.TableDefs(strTblName)
                     tbl.Connect = strConn
                     tbl.RefreshLink
                  End If
   
                  rs.MoveNext
               Wend
            End With
            CreateODBCLinkedTables = True
            MsgBox "Refreshed ODBC Data Sources", vbInformation
         CreateODBCLinkedTables_End:
            Exit Function
         CreateODBCLinkedTables_Err:
            MsgBox Err.Description, vbCritical, "MyApp"
            Resume CreateODBCLinkedTables_End
         End Function
   					

5. To test this function, type the following line in the Debug window, and then press ENTER:

   ?CreateODBCLinkedTables()
   						

   Note that you receive the message "Refreshed ODBC Data Sources." Also note that a new linked table called Authors exists in your database, and a new User DSN called Pubs exists in the ODBC Administrator in Control Panel.