WITH t1 AS(
    SELECT
        port_code AS "港コード",
        port_name AS "港名",
        SUM(CASE kind_code WHEN '110' THEN AMT ELSE 0 END) AS "入国者数",
        SUM(CASE kind_code WHEN '120' THEN AMT ELSE 0 END) AS "出国者数"
    FROM immigration
    JOIN port using(port_code)
    GROUP BY port_code, port_name
)

SELECT *,
    "入国者数" - "出国者数" AS "差分"
FROM t1
WHERE "入国者数" > "出国者数"
ORDER BY "入国者数" - "出国者数" DESC, "港コード" DESC