将表B中的某几列数据更新到表A中

declare
  a varchar2(20);
  b varchar2(20);
  c varchar2(20);
cursor mycur is
  select idnum,name,cardnum
  from 表B;
begin
  open mycur;
  loop
    fetch mycur into a,b,c;
    exit when mycur%notfound;
    update 表A set idnum = a,name = b where cardnum=c;
  end loop;
  close mycur;
end;