题解 | #计算用户的平均次日留存率#
计算用户的平均次日留存率
https://www.nowcoder.com/practice/126083961ae0415fbde061d7ebbde453
select count(distinct T2.device_id, T2.date) / count(distinct T1.device_id, T1.date) from question_practice_detail as T1 left join question_practice_detail as T2 on T1.device_id = T2.device_id and datediff (T2.date, T1.date) = 1;