Group a report based on a hierarchy level

Question

Hi,
I'm struggling with a query that I'd like to group a report based on the selection of a hierarchy level.
Here's the situation: I've got a table with a "normal" hierarchy, say the EMP table from SCOTT with its EMPNO and MGR columns. What I'd like to have is a report that gives me the sum of the SAL column group by all members on a given hierarchy level. So fi, if I choose LEVEL = 1, Id like to see the overall total, if I choose LEVEL = 2, I'd like to see the sum of salary of all employees managed by this respective manager etc.
I know that there are possibilities to denormalize the table first and try to solve it from there, but what I'd like to know is whether anybody is aware of a more generic way to achieve that? What I could accept is a hard coded limitation of the number of nested levels, as this seems to be very hard to achieve in SQL.
In the real scenario, I'm using only balanced trees, so from that point of view, the reports will be consistent.
Any ideas?
Thanks, Jürgen

Answer 1

select l, sum(salary) from (SELECT last_name, employee_id, manager_id, salary, LEVEL l
FROM employees
START WITH employee_id = 100
CONNECT BY PRIOR employee_id = manager_id) where l > :input_level
group by l;