select
IMMIGRATION.PORT_CODE as 港コード,
PORT.PORT_NAME as 港名,
sum(CASE
    WHEN GRP.GROUP_CODE = 110 THEN AMT
    ELSE 0
  END)as 入国者数,
sum(CASE
    WHEN GRP.GROUP_CODE = 120 THEN AMT
    ELSE 0
  END)as 出国者数,
'入国者数' - '出国者数' 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
group by
PORT.PORT_CODE,GRP.GROUP_CODE
order by 
差分 desc,港コード desc