SELECT
    IM1.PORT_CODE AS 港コード
    , PT.PORT_NAME AS 港名
    , IM1.AMT AS 入国者数
    , IM2.AMT AS 出国者数
    , (IM1.AMT - IM2.AMT) AS 差分 
FROM
    IMMIGRATION AS IM1
    INNER JOIN IMMIGRATION AS IM2 
        ON IM1.PORT_CODE = IM2.PORT_CODE 
        AND IM1.GROUP_CODE = IM2.GROUP_CODE 
        AND IM2.KIND_CODE = '120' 
    INNER JOIN PORT AS PT 
        ON IM1.PORT_CODE = PT.PORT_CODE 
WHERE
    IM1.GROUP_CODE = '120'
    AND IM1.KIND_CODE = '110'
    AND 差分 > 0 
ORDER BY
    差分 DESC
    , IM1.PORT_CODE DESC;