WITH OUT_AMT AS(
    SELECT
        PORT_CODE,
        AMT
    FROM
        IMMIGRATION
    WHERE
        GROUP_CODE = '120'
        AND KIND_CODE = '120'
)
SELECT
    IMMIGRATION.PORT_CODE AS 港コード,
    PORT.PORT_NAME AS 港名,
    IMMIGRATION.AMT AS 入国者数,
    OUT_AMT.AMT AS 出国者数,
    (IMMIGRATION.AMT - OUT_AMT.AMT) AS 差分
FROM
    IMMIGRATION
    INNER JOIN
        PORT ON PORT.PORT_CODE = IMMIGRATION.PORT_CODE,
        OUT_AMT ON OUT_AMT.PORT_CODE = IMMIGRATION.PORT_CODE
WHERE
    GROUP_CODE = '120'
    AND IMMIGRATION.KIND_CODE = '110'
    AND 入国者数 > 出国者数
ORDER BY
    差分 DESC,
    港コード DESC