with 入国 as(
    SELECT
        PORT_CODE
        ,AMT as 入国者数
    FROM
        IMMIGRATION
    WHERE
        GROUP_CODE = 120 AND
        KIND_CODE = 110
), 出国 as(
    SELECT
        PORT_CODE
        ,AMT as 出国者数
    FROM
        IMMIGRATION
    WHERE
        GROUP_CODE = 120 AND
        KIND_CODE = 120
), 入出国数 as(
    SELECT
        a.PORT_CODE
        ,入国者数
        ,出国者数
    FROM
        入国 as a
    INNER JOIN
        出国 as b
    ON
        a.PORT_CODE = b.PORT_CODE
)
SELECT
    tbl1.PORT_CODE as 港コード
    ,PORT_NAME as 港名
    ,入国者数
    ,出国者数
    ,(入国者数 - 出国者数) as 差分

FROM
    入出国数 as tbl1
INNER JOIN
    PORT as tbl2
ON
    tbl1.PORT_CODE = tbl2.PORT_CODE
WHERE
    差分 > 0
ORDER BY
    差分 DESC
    ,港コード DESC
;