WHERE DEPT_NO IS NOT
SELECT DEPT_NO, AVG (CURRENT_DATE - EMP_BDATE)
FROM EMP
WHERE DEPT_NO IS NOT NULL
GROUP BY DEPT_NO
HAVING NOT EXISTS (SELECT EMP1.DEPT_NO
FROM EMP EMP1
WHERE EMP1.DEPT_NO IS NOT NULL
GROUP BY EMP1.DEPT_NO
HAVING AVG (CURRENT_DATE - EMP1.EMP_BDATE) <
AVG (CURRENT_DATE - EMP.EMP_BDATE));
