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How To Use "DSN-Less" ODBC Connections with RDO and DAO


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Summary

With Microsoft Visual Basic versions 4.0, 5.0, and 6.0 for Windows, you can specify your ODBC (Open Database Connectivity) driver and server in your connect string when using RDO (Remote Data Object) and DAO (Data Access Objects) which eliminates the need to set up a DSN (Data Source Name). We call this a "DSN- Less" ODBC connection because you do not need to set up a DSN in order to access your ODBC database server.

To do this, you specify a "driver=" and "server=" parameter in your connect string as in the following example.

Note You must change Username= <username> and PWD =<strong password> to the correct values before you run this code. Make sure that Username has the appropriate permissions to perform this operation on the database.
   cnstr = "driver={SQL Server};server=myserver;" & _
     "database=mydb;Username=<username>;PWD=<strong password>;dsn=;"
   Set cn = en.OpenConnection("", False, False, cnstr)
				

NOTE: The driver name must be surrounded by curly brackets. For example: "{SQL Server}."

(CAUTION: DSN-Less connections will not work in Visual Basic 4.0 16-bit. If you try to use them you will get a General Protection Fault in module ODBC.DLL at 0006:080F.)

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More information

In Microsoft Visual Basic version 3.0 for Windows, you had to create a DSN that added an extra step when distributing your application because each workstation had to have the DSN created in order to access the specified server and database. This was done either manually with the ODBC Admin utility, through code with the RegisterDatabase function, or through code with the SQLConfigDatasource API function. For additional information on how to do this setup manually, please see the following articles in the Microsoft Knowledge Base:
123008 TITLE : How to Set Up ODBC Data Sources When Distributing an App

126940 : RegisterDatabase Fails After ODBC Version 2.x Installed

132329 : RegisterDatabase Method Does Not Modify ODBC.INI File

Sample Program

The following RDO example uses a "DSN-less" ODBC connection so you do not need to set up a DSN with the ODBC Admin utility beforehand.
  1. Start a new project in Visual Basic. Form1 is created by default.
  2. Add a command button to Form1, Command1 by default.
  3. Paste the following code into the General Declarations section of Form1.

    Note You must change Username= <username> and PWD =<strong password> to the correct values before you run this code. Make sure that Username has the appropriate permissions to perform this operation on the database.
          Dim en As rdoEnvironment
          Dim cn As rdoConnection
    
          Private Sub Form_Load()
            MousePointer = vbHourglass
            Dim strConnect As String
            ' Change the next line to reflect your driver and server.
            strConnect = "driver={SQL Server};server=jonfo5;" & _
              "database=pubs;Username=<username>;PWD=<strong password>;"
            Set en = rdoEngine.rdoEnvironments(0)
            Set cn = en.OpenConnection( _
              dsName:="", _
              Prompt:=rdDriverNoPrompt, _
              ReadOnly:=False, _
              Connect:=strConnect)
            cn.QueryTimeout = 600
            MousePointer = vbNormal
          End Sub
          Private Sub Command1_Click()
            MousePointer = vbHourglass
            Dim rs As rdoResultset
            Set rs = cn.OpenResultset(Name:="Select * from authors", _
              Type:=rdOpenForwardOnly, _
              LockType:=rdConcurReadOnly, _
              Options:=rdExecDirect)
            Debug.Print rs(0), rs(1), rs(2)
            MousePointer = vbNormal
          End Sub
    
    						
  4. Note that you must change your DRIVER, SERVER, DATABASE, UID, and PWD parameters in the OpenConnection method. You also need to modify the SQL statement contained in the Command1_Click event to match your own SQL data source.
  5. Check the Microsoft Remote Data Object in the Project References.
  6. Start the program or press the F5 key.
  7. Click the Command1 button to create a rdoResultset and display the first row of data in the debug window.

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References

Hitchhiker's Guide to Visual Basic and SQL Server, Microsoft Press.
ISBN: 1-55615-906-4.

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Keywords: KB147875, kbrdo, kbhowto

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Article Info
Article ID : 147875
Revision : 3
Created on : 8/30/2004
Published on : 8/30/2004
Exists online : False
Views : 558