DELETE FROM EMP
WHERE
    EMP_CODE IN (
        SELECT EMP.EMP_CODE
        FROM EMP
        JOIN EMP_INVALID AS INV
        ON EMP.EMP_CODE = INV.EMP_CODE
        WHERE
            NOT(EMP.VALID_FLG = '1' AND EMP.USER_UPDATE_DATETIME > INV.USER_UPDATE_DATETIME)
    );