select
 p.PORT_CODE as 港コード
,p.PORT_NAME as 港名
,sum(i1.AMT) as 入国者数
,sum(i2.AMT) as 出国者数
,sum(i1.AMT) - sum(i2.AMT) as 差分
from PORT p
join IMMIGRATION i1 on p.PORT_CODE = i1.PORT_CODE and i1.GROUP_CODE = '120' and i1.KIND_CODE = '110'
join IMMIGRATION i2 on p.PORT_CODE = i2.PORT_CODE and i2.GROUP_CODE = '120' and i2.KIND_CODE = '120'
group by p.PORT_CODE, p.PORT_NAME
having sum(i1.AMT) > sum(i2.AMT)
order by sum(i1.AMT) - sum(i2.AMT) desc, p.PORT_CODE desc