Question

I am trying to find a way to dynamically determine/reference a table name based on a value in another table.

In concept this is what I want:

SELECT * FROM TTestCase 
WHERE TTestCase.ElementNo = (
    SELECT TControlTables.ControlTable from TControlTables 
WHERE TControlTables.MessageType in (
    SELECT TTestCaseParameter.MessageType 
    FROM TTestCaseParameter).ElementNo

The “SELECT TControlTables.ControlTable from TControlTables
WHERE TControlTables.MessageType in (SELECT TTestCaseParameter.MessageType FROM TTestCaseParameter” is the query that determines which table’s ElementNo should be compared with the TestCase.ElementNo.

Answer 1

Some very rough notes, you will get much better code here http://msdn.microsoft.com/en-us/library/system.data.oledb.oledbcommand(v=vs.71).aspx. Hopefully, this will start you off.

    Dim tablename As String
    Dim cn As New OleDbConnection("connection here")
    cn.Open()
    Dim query = "SELECT TControlTables.ControlTable " _
              & "FROM TControlTables " _
              & "WHERE TControlTables.MessageType in (  " _
              & "SELECT TTestCaseParameter.MessageType " _
              & "FROM TTestCaseParameter)"

    Dim dc = New OleDbCommand(query, cn)
    Dim tname As OleDb.OleDbDataReader
    tname = dc.ExecuteReader

    If tname.HasRows Then
        tname.Read()
        tablename = tname("ControlTable")
        tname.Close()
        query = "SELECT * FROM TTestCase WHERE TTestCase.ElementNo = ( " _
              & "SELECT ElementNo FROM [" & tablename & "])"
        dc.CommandText = query
        Dim rows As OleDb.OleDbDataReader
        rows = dc.ExecuteReader

    End If