WITH IMM AS
(
    SELECT
        PORT_CODE, AMT AS "入国者数"
    FROM
        IMMIGRATION
    WHERE
        GROUP_CODE = '120'
        AND
        KIND_CODE = '110'
)
, EMM AS
(
    SELECT
        PORT_CODE, AMT AS "出国者数"
    FROM
        IMMIGRATION
    WHERE
        GROUP_CODE = '120'
        AND
        KIND_CODE = '120'
)

SELECT
    PORT.PORT_CODE AS "港コード"
    ,PORT.PORT_NAME AS "港名"
    ,IMM."入国者数"
    ,EMM."出国者数"
    ,IMM."入国者数" - EMM."出国者数" AS "差分"
FROM
    PORT
LEFT JOIN
    IMM ON PORT.PORT_CODE = IMM.PORT_CODE
LEFT JOIN
    EMM ON PORT.PORT_CODE = EMM.PORT_CODE
WHERE
    IMM."入国者数" > EMM."出国者数"
ORDER BY
    "差分" DESC
    ,"港コード" DESC