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 IM2.PORT_CODE = IM1.PORT_CODE 
        AND IM2.GROUP_CODE = IM1.GROUP_CODE 
        AND IM2.KIND_CODE = '120' 
    INNER JOIN PORT AS PT 
        ON PT.PORT_CODE = IM1.PORT_CODE
WHERE
    IM1.KIND_CODE = '110'
    AND 差分 > 0
    AND IM1.GROUP_CODE = '120'
ORDER BY
    差分 DESC,
    港コード DESC;