WITH master AS (
SELECT pr.PORT_CODE, AMT, PORT_NAME, GROUP_NAME, IIF(KIND_CODE = 110, AMT, 0) AS nyu, IIF(KIND_CODE = 120, AMT, 0) AS shutu
FROM IMMIGRATION im
LEFT JOIN PORT pr ON im.PORT_CODE = pr.PORT_CODE
LEFT JOIN GRP gr ON im.GROUP_CODE = gr.GROUP_CODE
WHERE GROUP_NAME='外国人'
)
SELECT PORT_CODE AS 港コード, PORT_NAME AS 港名, SUM(nyu) AS 入国者数	, SUM(shutu) AS 出国者数, SUM(nyu - shutu) AS 差分
FROM master
GROUP BY 1, 2
HAVING SUM(nyu - shutu) > 0
ORDER BY 5 DESC