with tmp as (
    select
    	P.PORT_CODE as 港コード
    	, P.PORT_NAME as 港名
    	, sum(case when I.KIND_CODE = '110' then AMT else 0 end) as 入国者数
    	, sum(case when I.KIND_CODE = '120' then AMT else 0 end) as 出国者数
    from PORT as P
    inner join IMMIGRATION as I using(PORT_CODE)
    where GROUP_CODE = '120'
    group by P.PORT_CODE
)
select
    *
    , 入国者数 - 出国者数 as 差分
from tmp
where 入国者数 > 出国者数
order by 差分 desc, 港コード desc;