题解 | #试卷发布当天作答人数和平均分#

select exam_id,
count(distinct uid) uv,
round(avg(score),1) avg_score
from user_info
join exam_record
using(uid)
join examination_info
using(exam_id)
where tag='SQL'
and day(start_time)=day(release_time)
and month(start_time)=month(start_time)
and year(submit_time)=2021
and level>=6
group by exam_id
order by uv desc,avg_score