SELECT 
    PORT.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
    INNER JOIN PORT
        ON IMMIGRATION.PORT_CODE = PORT.PORT_CODE
    INNER JOIN GRP
        ON IMMIGRATION.GROUP_CODE = GRP.GROUP_CODE
WHERE
    GROUP_NAME = "外国人"
GROUP BY PORT.PORT_CODE, 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