MYSQL数据库mysql 查询表中平均分最低的班级

drop table if exists dd;
create table dd (
user_id int ,
class_no int ,
score int
);
insert into dd values (1,1,1), (2,1,1), (3,1,2), (4,2,2);
select class_no ,avg(score)from dd group by class_no order by avg(score);