select
    p.PORT_CODE as 港コード,
    p.PORT_NAME as 港名,
    i.AMT as 入国者数,
    i2.AMT as 出国者数,
    ( i.AMT-i2.AMT) as 差分
from
    IMMIGRATION as i
inner join
    PORT as p on i.PORT_CODE = p.PORT_CODE
inner join
    IMMIGRATION as i2 on i.PORT_CODE = i2.PORT_CODE
    and i.GROUP_CODE = i2.GROUP_CODE
where
    i.GROUP_CODE = 120
and
    i.KIND_CODE = 110
and
    i2.KIND_CODE = 120
and
    差分 > 0
order by 差分 desc,港コード asc