题解 | #平均活跃天数和月活人数#
平均活跃天数和月活人数
http://www.nowcoder.com/practice/9e2fb674b58b4f60ac765b7a37dde1b9
select concat(substring_index(submit_time,'-',1), substring_index(substring_index(submit_time,'-',-2),'-',1)) month, ROUND(count(submit_time)/count(distinct uid),2) avg_active_days, count(distinct uid) mau from exam_record where year(submit_time)='2021' and submit_time is not null group by month

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