题解 | #任意两个连续自然月练题次数大于1的用户#
任意两个连续自然月练题次数大于1的用户
https://www.nowcoder.com/practice/a4cea6942a4f4354b0a0181aa5f446d2
select device_id from( select a.device_id,a.m m1,a2.m m2 from (select device_id,month(event_date) m,count(*) from question_practice_detail group by device_id,m having count(*)>1)a left join (select device_id,if(month(event_date)=1,13,month(event_date)) m,count(*) from question_practice_detail group by device_id,m having count(*)>1)a2 on a.device_id=a2.device_id and a.m=a2.m-1 where a2.m is not null )c order by device_id desc
用到了left join