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