select
    IM_IN.PORT_CODE as 港コード,
    P.PORT_NAME as 港名,
    sum(IM_IN.AMT) as 入国者数,
    sum(IM_OUT.AMT) as 出国者数,
    sum(IM_IN.AMT - IM_OUT.AMT) as 差分
from
    IMMIGRATION as IM_IN
    inner join
        IMMIGRATION as IM_OUT
        on
            IM_IN.PORT_CODE = IM_OUT.PORT_CODE
            and IM_OUT.KIND_CODE = '120'
    inner join
        PORT as P
        using(PORT_CODE)
    inner join
        GRP
        using(GROUP_CODE)
where
    IM_IN.KIND_CODE = '110'
    and IM_IN.AMT > IM_OUT.AMT
    and GRP.GROUP_CODE = '120'
group by
    IM_IN.PORT_CODE, P.PORT_NAME
order by
    差分 desc, 港コード desc ;