select
 PT.PORT_CODE as '港コード'
,PT.PORT_NAME as '港名'
,入国者数
,出国者数
,差分
from 
(select
     PORT_CODE
    ,sum(case
      when KIND_CODE = 110 then AMT
      else 0
     end) as '入国者数'
    ,sum(case
      when KIND_CODE = 120 then AMT
      else 0
     end) as '出国者数'
    ,sum(case
      when KIND_CODE = 110 then AMT
      else 0
     end)
    -sum(case
      when KIND_CODE = 120 then AMT
      else 0
     end) as '差分'
    from
     IMMIGRATION
    where GROUP_CODE = 120
    group by PORT_CODE
    ) as IM
,PORT as PT
where
 IM.PORT_CODE = PT.PORT_CODE
and 差分 > 0
order by
 差分 desc
,港コード desc