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