oracle批量更新多个字段

update table1 t1 
 set (a,b,c) = (select a,b,c from table2 t2 where t1.a=t2.a) 
where exists (select 1 from table2 t2 where t1.a=t2.a);

注意：加上where exists语句是为了避免将不匹配的记录更新为null