SELECT
    PORT.PORT_CODE AS '港コード'
    , PORT.PORT_NAME AS '港名'
    , IN_IMM.AMT AS '入国者数'
    , OUT_IMM.AMT AS '出国者数'
    , IN_IMM.AMT - OUT_IMM.AMT AS '差分'
FROM
    (
        SELECT
            PORT_CODE
            , AMT
        FROM
            IMMIGRATION
        WHERE
            KIND_CODE = '110'
            AND GROUP_CODE = '120'
    ) AS IN_IMM
    INNER JOIN (
        SELECT
            PORT_CODE
            , AMT
        FROM
            IMMIGRATION
        WHERE
            KIND_CODE = '120'
            AND GROUP_CODE = '120'
    ) AS OUT_IMM
        ON IN_IMM.PORT_CODE = OUT_IMM.PORT_CODE
    INNER JOIN PORT
        ON IN_IMM.PORT_CODE = PORT.PORT_CODE
WHERE
    IN_IMM.AMT - OUT_IMM.AMT > 0
ORDER BY
    差分 DESC
    , 港コード DESC