CODEWITHSUNDEEP
excelms-accessvbaodbc
AR.
AR.

Reputation: 40327

How can I best use VBA in Access or Excel to test an ODBC connection?

Given a pre-configured ODBC System DSN, I'd like to write a function that gracefully tests that connection using VBA.

Private Function TestConnection(ByVal dsnName As String) As Boolean

    ' What goes here?? '

End Function

Edit: To clarify, the System DSNs are pointing to external SQL Server 2005 databases, with Windows NT authentication.

One approach I've tried is to send some random query to the target database and catch the error. If the query works, return true. If there's an error then return false. This works just fine but it feels...kludgy. Is there a more elegant way, especially one that doesn't rely on On Error Goto ?

Note: It's a legacy Access 2000 database I'm working on, so any solution can't have any Access 2007 or 2003 dependencies. I'd like to make it generic to VBA, but if there's a simple way in Access that's fine too.

Much obliged for any advice.

Upvotes: 2

Views: 31736

Answers (4)

nepdev
nepdev

Reputation: 1

If you merely have to test that the database server is actually available, this can be done, despite what is being said here that it cannot.

In that case, you can attempt to open a TCP connection to the specific server and port. The default instance of SQL Server, for example, listens on TCP port 1433. Attempting a simple TCP connection in VBA will tell you if it succeeds or not. Only if that is successful I would query using the ODBC connection.

This is a lot more graceful and efficient. It would remove any "gross" error from your ODBC test code. However, as I said, it is only applicable if you need to test for the mere existence/availability of the database server instance.

Upvotes: 0

Nigel Heffernan
Nigel Heffernan

Reputation: 4726

I'm too late to give you a useful answer to your question, but I came here because I wanted to see if StaCkOverflow has a better answer than the code I'm currently using to test ADODB connections.

...It turns out that the answer is 'No', so I'll post the code for reference: someone else will find it useful.

Coding notes: this isn't a generic answer: it's a method from a class encapsulating the ADODB.Connection object, and it assumes the existence of object 'm_objConnect'.

TestConnection: a VBA Class method for publishing debugging information for an ADODB.Connection object

This prints out the connection string, the current status, a list of ADODB errors (if any) and a full listing of the onnection's named properties.




Public Sub TestConnection()
On Error GoTo ErrTest



Dim i As Integer



If m_objConnect Is Nothing Then



Debug.Print "Object 'm_objConnect' not instantiated."




Else



Debug.Print m_objConnect.ConnectionString
Debug.Print "Connection state = " & ObjectStateString(m_objConnect.State)

Debug.Print

If m_objConnect.Errors.Count > 0 Then
    Debug.Print "ADODB ERRORS (" & m_objConnect.Errors.Count & "):"
    For i = 0 To m_objConnect.Errors.Count
        With m_objConnect.Errors(i)
            Debug.Print vbTab & i & ":"  _ 
                      & vbTab & .Source & " Error " & .Number & ": " _ 
                      & vbTab & .Description & " " _ 
                      & vbTab & "(SQL state = " & .SqlState & ")"
        End With
    Next i
End If

Debug.Print

Debug.Print "CONNECTION PROPERTIES (" & m_objConnect.Properties.Count & "):"
For i = 0 To m_objConnect.Properties.Count - 1
    Debug.Print vbTab & i & ":" _ 
              & vbTab & m_objConnect.Properties(i).Name & " = " _ 
              & vbTab & m_objConnect.Properties(i).Value
Next i




End If



ExitTest:
    Exit Sub
ErrTest:
    Debug.Print "Error " & Err.Number & " raised by " & Err.Source & ": " & Err.Description
    Resume Next



End Sub



Private Function ObjectStateString(ObjectState As ADODB.ObjectStateEnum) As String



Select Case ObjectState
Case ADODB.ObjectStateEnum.adStateClosed
    ObjectStateString = "Closed"
Case ADODB.ObjectStateEnum.adStateConnecting
    ObjectStateString = "Connecting"
Case ADODB.ObjectStateEnum.adStateExecuting
    ObjectStateString = "Executing"
Case ADODB.ObjectStateEnum.adStateFetching
    ObjectStateString = "Fetching"
Case ADODB.ObjectStateEnum.adStateOpen
    ObjectStateString = "Open"
Case Else
    ObjectStateString = "State " & CLng(ObjectState) & ": unknown state number"
End Select



End Function

Share and enjoy: and watch out for line-breaks, helpfully inserted where they will break the code by your browser (or by StackOverflow's formatting functions).

Upvotes: 2

DJ.
DJ.

Reputation: 16257

There no magic function that will test this without actually connecting and trying an operation.

If you feel bad about the random query part - you can query the system tables

For Access

SELECT TOP 1 NAME FROM MSysObjects

For SQL Server

SELECT TOP 1 NAME FROM sysobjects

Upvotes: 0

shahkalpesh
shahkalpesh

Reputation: 33484


Dim cnn As ADODB.Connection
Dim canConnect as Boolean
Set cnn = New ADODB.Connection

cnn.Open "DSN HERE"
If cnn.State = adStateOpen Then
    canConnect = True
    cnn.Close
End If

Msgbox canConnect

EDIT: DSN Format could be "DSN=MyDSN;UID=myuser;PWD=myPwd;"
Look this for connection strings

Upvotes: 6

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