select
i.PORT_CODE as 港コード
,p.PORT_NAME as 港名
,sum(case when i.KIND_CODE = '110' then i.AMT else 0 end) as 入国者数
,sum(case when i.KIND_CODE = '120' then i.AMT else 0 end) as 出国者数
,sum(case when i.KIND_CODE = '110' then i.AMT else 0 end) - sum(case when i.KIND_CODE = '120' then i.AMT else 0 end) as 差分
from
IMMIGRATION i

join GRP g on i.GROUP_CODE = g.GROUP_CODE
join PORT p on i.PORT_CODE = p.PORT_CODE
where
g.group_name = '外国人'
group by i.PORT_CODE,p.PORT_NAME
having 差分 > 0
order by 差分 desc, 港コード desc