SELECT
    i.port_code AS 港コード
    , port_name AS 港名
    , MAX(CASE WHEN kind_code = 110 THEN amt END) AS 入国者数
    , MAX(CASE WHEN kind_code = 120 THEN amt END) AS 出国者数
    , MAX(CASE WHEN kind_code = 110 THEN amt END) - MAX(CASE WHEN kind_code = 120 THEN amt END) AS 差分
FROM
    immigration AS i
LEFT JOIN
    port AS p
ON
    i.port_code = p.port_code
WHERE
    group_code = 120
GROUP BY
    i.port_code
    , port_name
HAVING
    差分 > 0
ORDER BY
    差分 DESC
    , i.port_code DESC