Commonly refered to as a "groupwise max"
From: Jerry Schwartz [mailto:jschwartz@strippedm]
Sent: Friday, September 25, 2009 1:28 PM
Subject: Stupid GROUP BY question
It must be too late in the week…
Suppose table Cust has one field, CustID. Suppose table Notes has four fields: NoteID (unique), CustID, NoteTime, and NoteText.
A customer can have zero or more notes. Now here’s the seemingly simple problem that I’m trying to solve: I want to find the newest note (if any) for each customer.
If all I want is the date, then I can do
SELECT Cust.CustID, MAX(Notes.NoteTime) FROM Cust LEFT JOIN Notes ON Cust.CustID = Notes.Cust_ID GROUP BY Cust.CustID;
That will work just fine, but now I also want the NoteText associated with the newest note. Obviously I can’t use MAX(NoteText). I could do this using a temporary table, but it seems like there should be another way.
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