select
PORT.PORT_CODE as 港コード,
PORT.PORT_NAME as 港名,
sum(case when IMMIGRATION.KIND_CODE = "110" then IMMIGRATION.AMT end) as 入国者数,
sum(case when IMMIGRATION.KIND_CODE = "120" then IMMIGRATION.AMT end) as 出国者数,
sum(case when IMMIGRATION.KIND_CODE = "110" then IMMIGRATION.AMT end)
 - sum(case when IMMIGRATION.KIND_CODE = "120" then IMMIGRATION.AMT end) as 差分
from IMMIGRATION
inner join PORT
on IMMIGRATION.PORT_CODE = PORT.PORT_CODE
inner join GRP
on IMMIGRATION.GROUP_CODE = GRP.GROUP_CODE
where GRP.GROUP_NAME = "外国人"
group by PORT.PORT_CODE, PORT.PORT_NAME
having 差分 > 0
order by 差分 desc, 港コード desc