- select *
from Employee
where boss_id = x_id: Loop is driven by the
employees who work for x_id directly.
- return next e: Return one of those
employees, (i.e., append to the eventual output).
- return query: Also return
the employees who work for e
- select * from
works_for(e.emp_id): Recursive call, to get the
employees who work for e.emp_id, directly or indirectly.