SELECT
    PORT_CODE AS 港コード
    , PORT_NAME AS 港名
    , SUM(IIF(KIND_CODE = 110, AMT, 0)) AS 入国者数
    , SUM(IIF(KIND_CODE = 120, AMT, 0)) AS 出国者数
    , SUM(IIF(KIND_CODE = 110, AMT, 0))
        - SUM(IIF(KIND_CODE = 120, AMT, 0)) AS 差分
FROM
    IMMIGRATION
    INNER JOIN PORT
    USING (PORT_CODE)
    INNER JOIN GRP
    USING (GROUP_CODE)
WHERE
    GROUP_NAME = '外国人'
GROUP BY
    PORT_CODE, PORT_NAME
HAVING
    SUM(IIF(KIND_CODE = 110, AMT, 0)) > SUM(IIF(KIND_CODE = 120, AMT, 0))
ORDER BY
    SUM(IIF(KIND_CODE = 110, AMT, 0))
        - SUM(IIF(KIND_CODE = 120, AMT, 0)) DESC
    , PORT_CODE DESC