select
    p.port_code as 港コード,
    p.port_name as 港名,
    i_in.amt as 入国者数,
    i_out.amt as 出国者数,
    i_in.amt - i_out.amt as 差分
from
    immigration as i_in
    inner join port as p on i_in.port_code = p.port_code
    inner join immigration as i_out on i_in.port_code = i_out.port_code
    and i_out.group_code = i_out.group_code
    and i_out.kind_code = '120'
where
    i_in.group_code = '120'
    and i_in.kind_code = '110'
    and i_in.amt > i_out.amt
order by
    差分 desc,
    港コード asc;