Newbie question RE: Select common fields

Question

I have to select all common jobs from the emp table that are in dept's 10,20,30. Do I need to do a self join? Subquery? Any help will be greatly appreciate.

Answer 1

I can think of a couple of ways off the top of my head:
SELECT job_id
FROM employees e
WHERE department_id = 10 and
      EXISTS (SELECT 1 FROM employees i
              WHERE e.job_id = i.job_id and
                    i.department_id = 20) and
      EXISTS (SELECT 1 FROM employees i
              WHERE e.job_id = i.job_id and
                    i.department_id = 30);
SELECT job_id FROM employees
WHERE department_id = 10
INTERSECT
SELECT job_id FROM employees
WHERE department_id = 20
INTERSECT
SELECT job_id FROM employees
WHERE department_id = 30nurhidayat:
You query will return the jobs that are in the three departments, not the "common jobs" from the three departments.
Devanand:
Your query is is incorrect, it will throw:
ORA-00979: not a GROUP BY expression
because you do not have department in the select list
TTFN
John