SELECT
    a.PORT_CODE AS '港コード',
    a.PORT_NAME AS '港名',
    SUM(CASE WHEN i.KIND_CODE = '110' THEN i.AMT ELSE 0 END) AS '入国者数',
    SUM(CASE WHEN i.KIND_CODE = '120' THEN i.AMT ELSE 0 END) AS '出国者数',
    SUM(CASE WHEN i.KIND_CODE = '110' THEN i.AMT ELSE -i.AMT END) AS '差分'
FROM
    IMMIGRATION AS i
    INNER JOIN
        PORT AS a
    ON
        i.PORT_CODE = a.PORT_CODE
WHERE
    i.KIND_CODE IN ('110', '120')
GROUP BY
    a.PORT_CODE
HAVING
    差分 > 0
ORDER BY
    差分 DESC