题解 | #月总刷题数和日均刷题数#

select 
date_format(submit_time,'%Y%m')  submit_month,
count(*) as month_q_cnt,
round(count(*) / day(last_day(submit_time)) ,3)  avg_day_q_cnt
from practice_record 
where  year(submit_time) = '2021'
group by submit_month

union all 

select 
'2021汇总' as submit_month,
count(*) as month_q_cnt,
round(count(*) /31 ,3) as avg_day_q_cnt 
from practice_record 
where year(submit_time) = '2021' 
order by submit_month ;