题解 | #21年8月份练题总数#
21年8月份练题总数
https://www.nowcoder.com/practice/b8f30b239b454ed490367b53ea95607d
去重计数 distinct ，条件查询where
select
count(distinct device_id) did_cnt,
count(question_id) question_cnt
from
question_practice_detail
where
date_format(date,"%Y-%m")='2021-08';
