How do you return data from a function which can then be used in
a SELECT?

Here's a simplified version of what I'm trying to do. Basically, I'm
trying to select all employees which belong to group 10, *or* to any
subgroup of group 10.

SELECT employee_id FROM employee_table
WHERE employee_group = 10 OR employee_group IN
(
SELECT get_all_subgroups(10) FROM DUAL
)

The get_all_subgroups() function is written and it performs correctly,
except it returns its data as an ARRAY, which apparently isn't the correct
way to pass data back to a SELECT.

Thanks for any suggestions. I'm using Oracle, version 10g if that matters.

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