ACC2000: Procedure to Create Data Sources and Relink ODBC Tables (208295)

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Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements. 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 to 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:

   Table: tblODBCDataSources

   Field Name	Data Type	Field Size
   DataBase	Text	50
   UID	Text	50
   PWD	Text	50
   Server	Text	50
   ODBCTableName	Text	50
   LocalTableName	Text	50
   DSN	Text	50

   
   
3. Make the LocalTableName field the primary key, and save the table as tblODBCDataSources.
4. 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	sa
   PWD	<blank>
   Server	SQLPUBS
   ODBCTableName	dbo.authors
   LocalTableName	Authors
   DSN	Pubs

   
   
5. Create a module and type the following line in the Declarations section if it is not already there:

   Option Explicit

6. Type the following procedures:NOTE: The sample code in this article uses Microsoft Data Access Objects. For this code to run properly, you must reference the Microsoft DAO 3.6 Object Library. To do so, click References on the Tools menu in the Visual Basic Editor, and make sure that the Microsoft DAO 3.6 Object Library check box is selected.
   
   

   '***************************************************************
   '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 DAO.Database, tbl As DAO.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 DAO.Database, rs As DAO.Recordset, tbl As DAO.TableDef
      Dim strDSN as String
      ' ---------------------------------------------
      ' Register ODBC database(s).
      ' ---------------------------------------------
      Set db = CurrentDb
      Set rs = db.OpenRecordset("Select * From tblODBCDataSources Order By DSN")
      With rs
         While Not .EOF
            If strDSN <> rs("DSN") Then
               DBEngine.RegisterDatabase rs("DSN"), _
                     "SQL Server", _
                     True, _
                     "Description=VSS - " & rs("DataBase") & _
                     Chr(13) & "Server=" & rs("Server") & _
                     Chr(13) & "Database=" & rs("DataBase")
            End If
            strDSN = rs("DSN")
            ' ---------------------------------------------
            ' 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
   					

7. To test this function, type the following line in the Immediate 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.