select IG1.PORT_CODE AS 港コード
    , PORT.PORT_NAME AS 港名
    , IG1.AMT AS 入国者数
    , IG2.AMT AS 出国者数
    , IG1.AMT - IG2.AMT AS 差分
from IMMIGRATION AS IG1
    inner join IMMIGRATION AS IG2
    on IG1.PORT_CODE = IG2.PORT_CODE
    and IG1.GROUP_CODE = IG2.GROUP_CODE
    and IG2.KIND_CODE=120
    inner join PORT
    on IG1.PORT_CODE = PORT.PORT_CODE
where IG1.GROUP_CODE=120 and IG1.KIND_CODE=110 and 差分>0
order by 差分 desc
    , IG1.PORT_CODE desc;