SELECT
    PORT_CODE AS '港コード',
    PORT_NAME AS '港名',
    AMT_ENT AS '入国者数',
    AMT_DEP AS '出国者数',
    AMT_ENT - AMT_DEP AS '差分'
FROM (
    SELECT
        PORT_CODE,
        AMT AS AMT_ENT
    FROM
        IMMIGRATION
    WHERE
        KIND_CODE = '110'
) AS ENT
INNER JOIN (
    SELECT
        PORT_CODE,
        AMT AS AMT_DEP
    FROM
        IMMIGRATION
    WHERE
        KIND_CODE = '120'
) AS DEP USING (PORT_CODE)
INNER JOIN
    PORT USING (PORT_CODE)
WHERE
    AMT_ENT >= AMT_DEP
ORDER BY
    差分 DESC,
    PORT_CODE DESC
;