题解 | #异常的邮件概率#
异常的邮件概率
http://www.nowcoder.com/practice/d6dd656483b545159d3aa89b4c26004e
/先建个表，其中发送者为正常用户；接收者也是正常用户/
SELECT date,ROUND(AVG(case when type='completed' then 0
when type='no_completed' then 1
else null end),3)
FROM(
SELECT * FROM email
WHERE send_id IN (select id from user where is_blacklist=0)
and receive_id IN (select id from user where is_blacklist=0)
) u
group by date
order by date;
