SELECT
    *
FROM(

SELECT
    PORT_CODE AS '港コード',
    PORT_NAME AS '港名',
    SUM(CASE WHEN KIND_CODE = 110 THEN AMT END) AS '入国者数',
    SUM(CASE WHEN KIND_CODE = 120 THEN AMT END) AS '出国者数',
    SUM(CASE WHEN KIND_CODE = 110 THEN AMT END) - SUM(CASE WHEN KIND_CODE = 120 THEN AMT END) AS '差分'
FROM IMMIGRATION
LEFT JOIN PORT USING(PORT_CODE)
GROUP BY 1,2
)
WHERE "差分" > 0
ORDER BY "差分" DESC, "港コード" DESC