SELECT
    PORT_CODE AS '港コード'
    , PORT_NAME AS '港名'
    , x.AMT AS '入国者数'
    , y.AMT AS '出国者数'
    , x.AMT - y.AMT AS '差分'
FROM
    PORT
    INNER JOIN (
        SELECT
            *
        FROM
            IMMIGRATION
        WHERE
            GROUP_CODE = 120 -- 外国人
            AND KIND_CODE = 110 -- 入国
    ) AS x
        USING (PORT_CODE)
    INNER JOIN (
        SELECT
            *
        FROM
            IMMIGRATION
        WHERE
            GROUP_CODE = 120 -- 外国人
            AND KIND_CODE = 120 -- 出国
    ) AS y
        USING (PORT_CODE)
WHERE
    x.AMT > y.AMT
ORDER BY
    差分 DESC
    , 港コード DESC
;