题解 | #试卷发布当天作答人数和平均分#

select
    ei.exam_id,
    count(distinct ui.uid) as uv,
    round(avg(er.score),1) as avg_score
from
    exam_record er
    join examination_info ei on er.exam_id = ei.exam_id
    and date_format (ei.release_time, "%Y%m%d") = date_format (er.submit_time, "%Y%m%d")
    join user_info ui on er.uid = ui.uid
    and ui.level > 5
group by ei.exam_id
order by
    uv desc,
    avg_score asc

连表查询