Currently I have:
SELECT LCallRprt_Joind3.* FROM LCallRprt_Joind3 WHERE (((LCallRprt_Joind3.Timestamp)=(Select Max([Timestamp]) From LCallRprt_Joind3 as C Where C.Control_Number = LCallRprt_Joind3.Control_Number)));
LCallRprt_Joind3 is a union query with fields: Control_Number, PK, Timestamp, In/Out and Result.
I need the to select the most recent record for each Control_Number, and this query is really slow.
I'm trying to optimize the query, as I've noticed that the following runs seemingly instantaneously, with near the same results, but lacking fields: PK, In/Out, Result
SELECT Max(LCallRprt_Joind3.[timestamp]) AS TS, LCallRprt_Joind3.Control_Number FROM LCallRprt_Joind3 GROUP BY LCallRprt_Joind3.Control_Number;