How to nest the top-N capability?

Question

Okay, guys.  Here's a mind-bender for you.  Let's use an altered version of Oracle's EMP table.  Assume we add a "company number" column named CONO.  Thus, in the revised EMP table, each company has many departments, and each department has many employee salaries.  The objective is to print the total salaries by company.  The trick is to only sum the top-N salaries of each department.  Can any of you wizards crack this nut?
Thanks,
Kim
PS: If possible, please try to use the "with t as" syntax.

Answer 1

Hi,
I don't remember if I have modified by EMP table for some other tests anyway what I get running the following result in this 3 top salaries:
with got_rnk as
   select e.*,  rank() over (partition by cono order by sal desc) rnk 
     from emp e
select *
  from got_rnk
where rnk <=3;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO       CONO        RNK
      7839 KING       PRESIDENT            17-NOV-81       5000                    10          1          1
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20          1          2
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30          1          3
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20          2          1
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20          2          2
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10          2          3
6 rows selected.
Grouping by CONO result in the following:
with got_rnk as
   select e.*,  rank() over (partition by cono order by sal desc) rnk 
     from emp e
select cono, sum(sal) selected_sal
  from got_rnk
where rnk <=3
group by cono;
      CONO SELECTED_SAL
         1        10850
         2         8425
In case you have similar values for salary you may decide to use DENSE_RANK instead of RANK as already explained by Solomon in the other thread.
Also in the initial question you were asking:
The objective is to print the total salaries by company.  The trick is to only sum the top-N salaries of each department.
And it was not clear if you wanted to have the top N salary per department or per company.
Anyway after you have posted the output it was a bit more clear.
By the way, what's the difference with the question you posted yesterday??
It seems you are asking the same question but grouping by CONO instead of DEPTNO.
Regards.
Alberto
Message was edited by: AlbertoFaenza
Clarifications added