select 
  Y.港コード,
  Y.港名,
  T.inin as 入国者数,
  Y.outout as 出国者数,
  T.inin - Y.outout as 差分
from
(select
  PORT.PORT_CODE as 港コード,
  PORT.PORT_NAME as 港名,
  sum(AMT) as outout
from
  IMMIGRATION
inner join 
  PORT
on
  IMMIGRATION.PORT_CODE = PORT.PORT_CODE
where
  IMMIGRATION.GROUP_CODE = 120 and KIND_CODE = 120
group by
  PORT.PORT_NAME,KIND_CODE ) Y

inner join 

(select
  PORT.PORT_CODE as 港コード,
  PORT.PORT_NAME as 港名,
  sum(AMT) as inin
from
  IMMIGRATION
inner join 
  PORT
on
  IMMIGRATION.PORT_CODE = PORT.PORT_CODE
where
  IMMIGRATION.GROUP_CODE = 120 and KIND_CODE = 110
group by
  PORT.PORT_NAME,KIND_CODE ) T
on Y.港コード = T.港コード

order by 差分 DESC , Y.港コード DESC;
  
-- 差分の降順
-- 港コードの降順