SELECT p.PORT_CODE AS 港コード,
    PORT_NAME AS 港名,
    TOTAL(
        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
            WHEN KIND_CODE = "120" THEN - AMT
            ELSE 0
        END
    ) AS "差分"
FROM IMMIGRATION i
    INNER JOIN GRP g ON i.GROUP_CODE = g.GROUP_CODE
    INNER JOIN PORT p ON p.PORT_CODE = i.PORT_CODE
    WHERE g.GROUP_CODE = 120
GROUP BY p.PORT_CODE,
    p.PORT_NAME

HAVING "差分" > 0
ORDER BY "差分" DESC,
    p.PORT_CODE DESC