How to select top x records for every group

问题

I tried something like this

select Id,UserId from myTable group by Id,UserId having COUNT(UserId)<7

Now what i want to do is selecting 6 records for each userid. But my approach failed.

So what is the correct syntax ?

Id is primary key clustered index

回答1:

This should get you pretty close

WITH    r ( userid, rnk )
      AS ( SELECT   userid, RANK() OVER ( PARTITION BY id ) AS rnk
           FROM     MyTable 
           GROUP BY userid)
SELECT  r.*
FROM    r
WHERE   r.Rank <= 6 

来源：https://stackoverflow.com/questions/14025255/how-to-select-top-x-records-for-every-group