题解 | #异常的邮件概率#
异常的邮件概率
https://www.nowcoder.com/practice/d6dd656483b545159d3aa89b4c26004e
select date,round(sum(a.c)/count(date),3) from (select *,case when type like 'c%' then 0 else 1 end c from email) a where send_id not in (select id from user where is_blacklist = 1) and receive_id not in (select id from user where is_blacklist = 1) group by date