SELECT 
    IM.PORT_CODE AS 港コード
    , PT.PORT_NAME AS 港名
    , SUM(CASE WHEN KIND_CODE = '110' THEN AMT ELSE 0 END) AS "入国者数"
    , SUM(CASE WHEN KIND_CODE = '120' THEN AMT ELSE 0 END) AS "出国者数"
    , SUM((CASE WHEN KIND_CODE = '110' THEN AMT ELSE 0 END) - 
        (CASE WHEN KIND_CODE = '120' THEN AMT ELSE 0 END)) AS "差分"
FROM 
    IMMIGRATION AS IM
    INNER JOIN PORT AS PT 
        ON IM.PORT_CODE = PT.PORT_CODE
    INNER JOIN GRP 
        ON IM.GROUP_CODE = GRP.GROUP_CODE 
        AND IM.GROUP_CODE = '120' -- 外国人
GROUP BY 
    IM.PORT_CODE
HAVING 
    "差分" > 0
ORDER BY 
    "差分" DESC, IM.PORT_CODE DESC
;