select
  PORT.PORT_CODE as 港コード,
  PORT.PORT_NAME as 港名,
  IM_IN.AMT as 入国者数,
  IM_OUT.AMT as 出国者数,
  IM_IN.AMT - IM_OUT.AMT as 差分
from
  (
   select
     PORT_CODE,
     AMT
   from
     IMMIGRATION
   where
     KIND_CODE = '110'
     and GROUP_CODE = '120'
   ) as IM_IN
join
  (
   select
     PORT_CODE,
     AMT
   from
     IMMIGRATION
   where
     KIND_CODE = '120'
     and GROUP_CODE = '120'
   ) as IM_OUT
  on IM_IN.PORT_CODE = IM_OUT.PORT_CODE
join PORT
  on IM_IN.PORT_CODE = PORT.PORT_CODE
where
  入国者数 > 出国者数
order by
  差分 desc,
  港コード desc