题解 | #计算用户的平均次日留存率#
SQL类别高难度试卷得分的截断平均值
http://www.nowcoder.com/practice/a690f76a718242fd80757115d305be45
SELECT
count(DISTINCT device_id) as did_cnt,
count(question_id) as question_cnt
from question_practice_detail
where year(date)= 2021 and month(date)=8
