with subq as 
(
select PORT_CODE as 港コード
	,sum(case when KIND_CODE = '110' then AMT else 0 end) as 入国者数
	,sum(case when KIND_CODE = '120' then AMT else 0 end) as 出国者数

from IMMIGRATION
where GROUP_CODE = '120' --'外国人'
group by PORT_CODE
)

select 港コード
	,B.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 subq A
left outer join PORT B
on A.港コード = B.PORT_CODE
where 入国者数 > 出国者数
order by 差分 desc ,港コード desc