TOP N problem with GROUP BY clause

问题

The problem: I need to find all active [GiftPledges] that have the last three [GiftDetails] have a zero amount.

SELECT gp.PledgeId FROM GiftPledge gp
      INNER JOIN GiftDetail gd ON gp.PledgeId = gd.PledgeId
      WHERE gp.PledgeStatus = 'A'
      GROUP BY PledgeId
      HAVING COUNT(PledgeId) >= 3

Now, I have all my [GiftPledges] that have at least three [GiftDetails].

SELECT TOP 3 gdi.Amt FROM GiftDetail gdi
      INNER JOIN GiftHeader ghi ON gdi.GiftRef = ghi.GiftRef
      WHERE gdi.PledgeId = gp.PledgeId
      ORDER BY ghi.GDate DESC

This gives me the three most recent [GiftDetails] associated with a given [GiftPledge]. The problem is that I don't know how to sum the second query and have it be a part of the WHERE clause in the first query.

I found this article about "Top n per Group" and that seems like the direction I need to be headed, but I'm not sure I'm on the right track.

Any help, clarifications or suggestions would be greatly appreciated.

回答1:

SELECT gp.PledgeId FROM GiftPledge gp
      INNER JOIN GiftDetail gd ON gp.PledgeId = gd.PledgeId
      WHERE gp.PledgeStatus = 'A'
      GROUP BY PledgeId
      HAVING COUNT(PledgeId) >= 3 
AND
GP.PledgeID in (
SELECT PledgeID From
(
SELECT TOP 3 gp.PledgeID, gdi.Amt  FROM GiftDetail gdi
      INNER JOIN GiftHeader ghi ON gdi.GiftRef = ghi.GiftRef
      WHERE gdi.PledgeId = gp.PledgeId
      ORDER BY ghi.GDate DESC
) x_amt 
Group By PledgeID
Having SUM(AMT) ) x_sum = 0

something like that anyway.

来源：https://stackoverflow.com/questions/757763/top-n-problem-with-group-by-clause

标签

tsql

select

group-by

greatest-n-per-group