select
 PORT.PORT_CODE as 港コード
,PORT.PORT_NAME as 港名
,nyukoku.AMT as 入国者数
,syukkoku.AMT as 出国者数
,cast(nyukoku.AMT as REAL) - cast(syukkoku.AMT as REAL) as 差分
from
(select IMMIGRATION.PORT_CODE,IMMIGRATION.AMT
from IMMIGRATION inner join GRP on
 IMMIGRATION.GROUP_CODE = GRP.GROUP_CODE
 and IMMIGRATION.KIND_CODE = '110'
 and GRP.GROUP_CODE = '120') nyukoku
inner join
(select IMMIGRATION.PORT_CODE,IMMIGRATION.AMT
from IMMIGRATION inner join GRP on
 IMMIGRATION.GROUP_CODE = GRP.GROUP_CODE
 and IMMIGRATION.KIND_CODE = '120'
 and GRP.GROUP_CODE = '120') syukkoku
on nyukoku.PORT_CODE = syukkoku.PORT_CODE
 and nyukoku.AMT > syukkoku.AMT
inner join PORT on nyukoku.PORT_CODE = PORT.PORT_CODE
order by 差分 desc,PORT.PORT_CODE desc;