>How could your collegue get the results? It's an impossible query. If you have 2 records with the same ID (MAPREF) and the same date and your question is "give me the record with the greatest date" then the only answer is to return both or neither. returning just one is not necessraily the "greatest date" because they both have the exact same date. There has to be more criteria to return just one record if both your current criteria fields are equal.

She added other fields into the file, which already had maximum date, then somehow run an update query. I haven't asked her details yet.

The problem is, what even if I don't have duplicates in the original file (I group by MapRef and LstSlDate), it still can not produce the desired result by joining mapref and LstSlDate for empty LstSlDate...