题解 | #月总刷题数和日均刷题数#

select 
date_format(submit_time,'%Y%m') submit_month,
count(question_id) month_q_cnt,
round(count(question_id)/day(last_day(max(submit_time))),3) avg_day_cnt
from practice_record
where year(submit_time) =2021
group by date_format(submit_time,'%Y%m')
union
select "2021汇总",count(question_id),
round(count(question_id)/31,3)
from practice_record
where year(submit_time)=2021
order by submit_month