WITH im_table AS (
    SELECT
        im.port_code AS '港コード',
        pt.port_name AS '港名',
        sum(
            CASE
                WHEN kind_code = 110 THEN im.amt
                ELSE 0
            END
        ) AS '入国者数',
        sum(
            CASE
                WHEN kind_code = 120 THEN im.amt
                ELSE 0
            END
        ) AS '出国者数'
    FROM
        immigration AS im
        INNER JOIN port AS pt ON im.port_code = pt.port_code
    WHERE
        im.group_code = 120
    GROUP BY
        im.port_code
)
SELECT
    *,
    (入国者数 - 出国者数) AS '差分'
FROM
    im_table
WHERE
    入国者数 > 出国者数
ORDER BY
    差分 DESC,
    港コード DESC