SELECT
    IM1.PORT_CODE AS 港コード,
    PO.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 IM1.GROUP_CODE = "120"
        AND IM1.KIND_CODE = "110"
        AND IM2.KIND_CODE = "120"
    INNER JOIN PORT AS PO
        ON IM1.PORT_CODE = PO.PORT_CODE
WHERE 
    IM1.AMT - IM2.AMT > 0
ORDER BY
    差分 DESC,
    IM1.PORT_CODE DESC;