select
    p.port_code 港コード
    ,p.port_name 港名
    ,i1.amt 入国者数
    ,i2.amt 出国者数
    ,i1.amt - i2.amt 差分
from
    (select
        port_code
        ,amt
     from
        immigration
    where
        group_code = '120'
        and kind_code = '110') i1 
join
    port p
on
    i1.port_code = p.port_code
join
    (select
        port_code
        ,amt
     from
        immigration
    where
        group_code = '120'
        and kind_code = '120') i2
on
    i2.port_code = p.port_code
order by
    差分 desc, p.port_code desc;