Terminating Query If Not Connection - sql

Question

I have a code that uploads data to a SQL server database, I am trying to add in an IF line of code saying if there is a connection then to continue, but if there is not a connection then to END. I am having a difficult time figuring out the wording and placement though. The beginning of the code that connects is:
Public Function Update()
Dim cdb As DAO.Database, qdf As DAO.QueryDef
Dim rs As DAO.Recordset
Dim err As DAO.Error
Const ConnectionString = _
"ODBC;" & _
"Driver={SQL Server Native Client 10.0};" & _
"Server=SERV;" & _
"Database=DB;" & _
"UID=ID;" & _
"PWD=PWD;"
Set cdb = CurrentDb
Set qdf = cdb.CreateQueryDef("")
Set rs = CurrentDb.OpenRecordset("CDData", dbOpenTable)
qdf.Connect = ConnectionString
Do While Not rs.EOF

Answer 1

While one can simple attempt to execute any query or command, the “time out” and delay to test for an active connection can result in a VERY LONG delay. As a result a wonderful trick exists that uses a DIFFERENT connection mechanism in Access and thus “reduces” the potential VERY long delay when attempting to use a saved query that is based on linked tables. (that "different" connection system occurs when you create a queryDef as opposed to a linked table or a query based on a linked table to sql server)
The follow code will return true or false if you have a working SQL connection:
Function TestLogin(strcon As String) As Boolean
On Error GoTo TestError
Dim dbs As DAO.Database
Dim qdf As DAO.QueryDef
Set dbs = CurrentDb()
Set qdf = dbs.CreateQueryDef("")
qdf.Connect = strcon
qdf.ReturnsRecords = False
'Any VALID SQL statement that runs on server will work below.
qdf.SQL = "SELECT 1 as test"
qdf.Execute
TestLogin = True
Exit Function
TestError:
TestLogin = False
Exit Function
End Function
So in code you now with your connection string code go:
If TestLogIn(strConn) = false then
msgbox "no connection or logon invalid"
exit sub
End If
' record processing code goes here for successful logon/connection.