/*(35)建立一个存储过程，输入一个学生的姓名，返回该学生全部必修课课程的平均成绩。*/
drop procedure if exists ppp;
delimiter $$
create procedure ppp(
$name varchar(20),
out $avg decimal(10,2)
)
begin
with tmp as(
select avg(score) avg from grades a
join courses b using(courseid)
where a.studentid=(select studentid from students where name=$name)
and b.majors='' or b.majors like '%a%')
select cast(avg as decimal(10,2)) into $avg from tmp;
end $$
delimiter ;
call ppp('陈蓉',@avg);
select @avg;

有哪位大神知道这个提示是什么意思吗？这道题该咋写啊