Question

Possible Duplicate:
Selecting the top n rows within a group by clause

I have the following data:

id actionid commentid 
1  1        1 
2  1        2
3  1        3
4  2        1 

I want to create a sql to only show the top 2 comments for each actionid. In that case I the sql should only return id (1,2,4)

Thanks

Answer 1

SELECT id, 
       actionid, 
       commentid
FROM (
   SELECT id, 
          actionid, 
          commentid, 
          row_number() over (partition by actionid order by id) rn
   FROM your_table
) t
WHERE rn <= 2