SELECT
    I1.PORT_CODE AS 港コード
    , P.PORT_NAME AS 港名
    , I1.AMT AS 入国者数
    , I2.AMT AS 出国者数
    , (I1.AMT - I2.AMT) AS 差分 
FROM
    IMMIGRATION I1 
    INNER JOIN 
    IMMIGRATION I2 
    ON
    I2.PORT_CODE = I1.PORT_CODE 
    AND 
    I2.GROUP_CODE = I1.GROUP_CODE 
    AND 
    I2.KIND_CODE = '120' 
    INNER JOIN PORT AS P 
        ON P.PORT_CODE = I1.PORT_CODE 
WHERE
    I1.GROUP_CODE = '120' 
    AND I1.KIND_CODE = '110' 
    AND 差分 > 0 
ORDER BY
    差分 DESC
    , I1.PORT_CODE DESC;