SELECT
    PORT_CODE AS 港コード
    ,PORT_NAME AS 港名
    ,ENTRANTS AS 入国者数
    ,DEPARTURES AS 出国者数
    ,(ENTRANTS - DEPARTURES) AS 差分
FROM
    (SELECT
        IM.PORT_CODE
        ,PO.PORT_NAME
        ,SUM(CASE
            WHEN IM.KIND_CODE = '110' THEN AMT
            ELSE 0
        END) AS ENTRANTS
        ,SUM(CASE
            WHEN IM.KIND_CODE = '120' THEN AMT
            ELSE 0
        END) AS DEPARTURES
    FROM
        IMMIGRATION AS IM
        inner join PORT AS PO
            ON PO.PORT_CODE = IM.PORT_CODE
    WHERE
        IM.GROUP_CODE = '120'
    GROUP BY
        IM.PORT_CODE
        ,PO.PORT_CODE
    ) AS IM2
WHERE
    ENTRANTS > DEPARTURES
ORDER BY
    差分 DESC
    ,PORT_CODE DESC