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