--更新高价件表中的型号, hm_material h1
update hm_highrate_material h
   set h.material_model = （select h1.model from hm_material h1
 where h.material_id = h1.material_id);

--对表A的a2，a3进行更新（带条件）；
update A
   set (A.a2, A.a3) =
       (select B.b2, b.b3
          from B
         where B.b1 = A.a1 and A.a3 = 100)
 where exists (select 'X'
          from B
         where B.b1 = A.a1 and A.a3 = 100);
 
 
--或者： 
update A
   set (A.a2, A.a3) =
       (select B.b2, b.b3
          from B
         where B.b1 = A.a1 and A.a3 = 100)
       　　where A.a1 in (select B.b1
                           from B
                          where B.b1 = A.a1 and A.a3 = 100);