문제
정답
SELECT employee_id FROM Employees WHERE employee_id NOT IN (SELECT employee_id FROM Salaries)
UNION
SELECT employee_id FROM Salaries WHERE employee_id NOT IN (SELECT employee_id FROM Employees)
ORDER BY employee_id ASC
SELECT employee_id FROM Employees WHERE employee_id NOT IN (SELECT employee_id FROM Salaries)
UNION
SELECT employee_id FROM Salaries WHERE employee_id NOT IN (SELECT employee_id FROM Employees)
ORDER BY employee_id ASC