注意事项：

1、当前日期的表达：因为题目里的日期是短日期，因此用curdate()，如果是长日期，则用now()

2、根据subject_id升序排列：因为name和subject_id一一对应，所以用name,subject_id分组，此时就可以用subject_id进行排序

select t1.name,t1.cnt from (
select s.name,s1.subject_id,count(*) as cnt from submission as s1
left join subject as s 
on s1.subject_id = s.id 
where s1.create_time = curdate()
group by s.name,s1.subject_id order by count(*) desc,s1.subject_id asc 
) t1