I effectively have 2 queries which I am trying to make into 1, I am trying to get the trayNos that exist in the first query
IE 1 2 3 4 but do not appear in the second query, so I am looking for the query to return TrayNos 2 3 4. I hope this makes sense.
from Session, Count
where (Session.Session_ID = Count.Session_ID) /* 1 2 3 4 */
where (NOT EXISTS
where (Session.Session_ID = Count.Session_ID))) /* 1 1 1 */