select
    "港コード",
    "港名",
    "入国者数",
    "出国者数",
    "入国者数" - "出国者数" as "差分"
from
    (
        select
            P.PORT_CODE as "港コード",
            P.PORT_NAME as "港名",
            sum(
                case
                    when I.KIND_CODE == "110" then I.AMT
                    else 0
                end
            ) as "入国者数",
            sum(
                case
                    when I.KIND_CODE == "120" then I.AMT
                    else 0
                end
            ) as "出国者数"
        from
            GRP as G,
            IMMIGRATION as I,
            PORT as P
        where
            P.PORT_CODE == I.PORT_CODE
            and G.GROUP_CODE == I.GROUP_CODE
            and G.GROUP_NAME == "外国人"
        group by
            P.PORT_CODE
    )
where
    "入国者数" > "出国者数"
order by
    "差分" desc,
    "港コード" desc