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