这SQL是啥！啥！啥！惨痛

update un u
   set u.reserve = 0, u.cnt = u.cnt + u.share,u.modified=sysdate
where exists ( select 'X'
          from tb t, un u
         where t.type_id = 21
           and t.order_id = u.united_id
           and t.status = 8 );