题解 | #月总刷题数和日均刷题数#

select 
	date_format(submit_time, '%Y%m') submit_month, 
	count(submit_time) month_q_cnt, 
	round(count(submit_time) / Day(LAST_DAY(Min(submit_time))), 3) avg_day_q_cnt
from practice_record
where year(submit_time) = '2021'
group by date_format(submit_time, '%Y%m')
union all
select 
	'2021汇总' as submit_month, 
	count(submit_time) month_q_cnt, 
	round(count(submit_time) / 31, 3) avg_day_q_cnt
from practice_record
where year(submit_time) = '2021'
order by submit_month