SELECT
    RET.PORT_CODE as "港コード"
    ,PRT.PORT_NAME as "港名"
    ,A AS "入国者数"
    ,B AS "出国者数"
    ,(A-B) AS "差分"
FROM
    (
    SELECT
        PORT_CODE,
        SUM(IIF(KIND_CODE='110', AMT, 0)) AS A,
        SUM(IIF(KIND_CODE='120', AMT, 0)) AS B
    FROM
        (
        SELECT
            PORT_CODE,
            KIND_CODE,
            SUM(AMT) as AMT
        FROM IMMIGRATION 
        WHERE GROUP_CODE = '120'
        GROUP BY PORT_CODE, KIND_CODE
        ) IM
    GROUP BY PORT_CODE
    ) RET
    INNER JOIN PORT PRT ON RET.PORT_CODE = PRT.PORT_CODE
WHERE A>B
ORDER BY 
差分 desc, RET.PORT_CODE Desc