SELECT
    IMG.PORT_CODE AS "港コード"
    , PORT.PORT_NAME AS "港名"
    , IMG.AMT AS 入国者数
    , IMG2.AMT AS 出国者数
    , IMG.AMT - IMG2.AMT AS "差分"
FROM
    IMMIGRATION AS IMG
    JOIN IMMIGRATION AS IMG2
    ON IMG2.PORT_CODE = IMG.PORT_CODE
    AND IMG2.KIND_CODE = "120"
    AND IMG2.GROUP_CODE = "120"
    JOIN PORT ON PORT.PORT_CODE = IMG.PORT_CODE
WHERE
    IMG.GROUP_CODE = 120
    AND IMG.KIND_CODE = 110
    AND 差分 > 0
ORDER BY
    差分 DESC,
    港コード DESC
;