select 
PORT.PORT_CODE AS 港コード,
PORT.PORT_NAME AS 港名,
sum(IM_IN.AMT) AS 入国者数,
sum(IM_OUT.AMT) AS 出国者数,
sum(IM_IN.AMT) - sum(IM_OUT.AMT) AS 差分

from PORT

left join IMMIGRATION IM_IN
on 	IM_IN.PORT_CODE = PORT.PORT_CODE
and IM_IN.KIND_CODE = '110'

left join IMMIGRATION IM_OUT
on  IM_OUT.PORT_CODE = PORT.PORT_CODE
and IM_OUT.KIND_CODE = '120'

left join GRP
on  IM_IN.GROUP_CODE = GRP.GROUP_CODE
and IM_OUT.GROUP_CODE = GRP.GROUP_CODE
and GRP.GROUP_CODE = '120'

where IM_IN.AMT > IM_OUT.AMT

group by PORT.PORT_CODE, PORT.PORT_NAME

order by 差分 desc, PORT.PORT_CODE desc