DELETE FROM EMP
WHERE
 EMP_CODE IN
 ( SELECT
   A.EMP_CODE
  FROM
   EMP A 
  LEFT OUTER JOIN EMP_INVALID B
  ON A.EMP_CODE = B.EMP_CODE
  WHERE
   A.VALID_FLG = '0'OR
   (A.VALID_FLG = '1' AND
    A.USER_UPDATE_DATETIME <= B.USER_UPDATE_DATETIME));