SELECT
    IM.PORT_CODE AS 港コード
    ,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) - SUM(CASE WHEN KIND_CODE = '120' THEN AMT ELSE 0 END) AS 差分
FROM 
    IMMIGRATION AS IM
LEFT OUTER JOIN
    GRP
ON
    IM.GROUP_CODE = GRP.GROUP_CODE
LEFT OUTER JOIN
    PORT
ON
    IM.PORT_CODE = PORT.PORT_CODE
WHERE
    IM.GROUP_CODE = '120'
GROUP BY
    IM.PORT_CODE
    ,PORT.PORT_NAME
HAVING
    SUM(CASE WHEN KIND_CODE = '110' THEN AMT ELSE 0 END) - SUM(CASE WHEN KIND_CODE = '120' THEN AMT ELSE 0 END) > 0
ORDER BY
    差分 DESC
    ,港コード DESC