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