SQL: Select maximum value for each unique key?

Question

Sorry, I\'m not sure how to phrase that and I\'m really not very good with SQL. The db engine i SQL Server Compact. I currently have this query:

SELECT *
FRO         


        

Answer 1

Here's how I would do it:

SELECT s1.*
FROM Samples s1
LEFT JOIN Samples s2 
  ON (s1.Thread = s2.Thread and s1.HitCount < s2.HitCount)
WHERE s1.FunctionId NOT IN (SELECT CalleeId FROM Callers) 
  AND s2.Thread IS NULL
ORDER BY s1.ThreadId, s1.HitCount DESC

In other words, the row s1 for which there is no other row s2 matching the same Thread and having a greater HitCount.