with 구문 샘플

SELECT DEPTNO,
       (SELECT COUNT(*) -- 1 레벨
          FROM (SELECT DEPTNO
                  FROM DEPT C -- 2 레벨
                 WHERE A.DEPTNO = C.DEPTNO
                 GROUP BY DEPTNO
                ) B, EMP E
         WHERE E.DEPTNO = B.DEPTNO
        ) CNT
FROM DEPT A;

SELECT DEPTNO,
       (WITH
        DEPT_TEST AS (
                      SELECT DEPTNO
                        FROM DEPT
                       GROUP BY DEPTNO )
        SELECT COUNT(*)
          FROM DEPT_TEST B, EMP E
         WHERE B.DEPTNO = E.DEPTNO
           AND A.DEPTNO = B.DEPTNO
       ) CNT
FROM DEPT A;