Top 20 (details) for top 20 (summary)

Question

I have a query whose structure is somewhat like:
select distinct c,t, cu, s, somenumber, all
from
(-- outermost
    SELECT 
    t, c, cu,somenumber,all,c_cd, cname
    FROM ...
    where ...
    and c_cd in 
                   (--1st
                    select c_cd from
                        (--2nd
                        select c_cd, name,somenumber,ALL
                        from
                        (-- 3rd
                           SELECT c_cdc cname,
                           ...m,
                            sum(o) ALL
                            FROM
                            where
                            group by c_cd, cname
                            ORDER BY somenumber desc
                        )-- 3rd
where rownum <=20
                        )-- 2nd
                        )-- 1st                    
group by t,cu, c_cd, cname
order by somenumber desc
)-- outermost
where rownum <=20 -- this wont return top 20 per c_cd because no group by. How can I get top 20 details (outer query) for top 20 summary c_cd's (summary inner query)
order by somenumber desc what I am trying to do here is:
the inner query returns 20 c_cd's. The outer (main) query returns to 20 details (by somenumber) for that 10 cd_s.
However I am not able to say that give me the top 10 details for the give 20 c_cd's.
It is like give me top 20 based on somenumber group by the given top 20 c_cd's.
Any idea how can I modify my query and get the results?

Answer 1

Is there some reason you can't accomplish what you want, far more easily, using analytic functions?
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