题解 | 被重复观看次数最多的3个视频
select cid,pv,
row_number() over(order by pv desc,release_date desc) as rk
from(
select cid, sum(cnt) as pv -- 每个视频观看次数
from(
select cid,uid,count(uid) cnt -- 每个视频每个人看了几次
from play_record_tb
group by cid,uid
having cnt <> 1
)t1
group by cid
) t2
left join course_info_tb using(cid)
limit 3
