delete from EMP 
where
    EMP_CODE in (
    select
        P.EMP_CODE
    from
        EMP P
        inner join
            EMP_INVALID S
            on
            P.EMP_CODE=S.EMP_CODE
    where
        P.VALID_FLG <> '1'
        or
        (P.VALID_FLG ='1'
        and P.USER_UPDATE_DATETIME <= S.USER_UPDATE_DATETIME -- EMP_INVALIDの更新が後
        )
    )