① EXISTS 사용

입력

    SELECT department_id, department_name
      FROM departments a
     WHERE EXISTS ( SELECT *
                     FROM employees b
                    WHERE a.department_id = b.department_id
                      AND b.salary > 3000)
    ORDER BY a.department_name;

결과

    DEPARTMENT_ID  DEPARTMENT_NAME
    ------------- ---------------------------------
    60             IT
    110            경리부
    30             구매/생산부
    90             기획부
    ...
    11 개의 행이 선택됨.