SELECT
t1.PORT_CODE as 港コード,
t2.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(select
        port_code,
        sum(case when group_code = "120" and kind_code = "110" then AMT else 0 end) as 入国者数,
        sum(case when group_code = "120" and kind_code = "120"  then AMT else 0 end) as 出国者数
        from IMMIGRATION
        group by port_CODE
) as t1

left outer join

PORT as t2
on t1.port_code = t2.port_code
where 差分 > 0
order by 差分 desc, 港コード desc