with t as (
select 
PORT_CODE 港コード,
PORT_NAME 港名, 
sum(iif(KIND_CODE=110,AMT,0))入国者数,
sum(iif(KIND_CODE=120,AMT,0))出国者数,
sum(iif(KIND_CODE=110,AMT,0)) - sum(iif(KIND_CODE=120,AMT,0)) 差分
from 
    IMMIGRATION
    natural join PORT
    natural join GRP
where 
    GROUP_CODE=120
group by 1,2
)

select 
*
from t
where
    入国者数 > 出国者数
order by 5 desc,1 desc