题解 | 被重复观看次数最多的3个视频
select a.cid,sum(a.cishu),row_number() over(order by sum(a.cishu) desc,max(c.release_date) desc) rk
from (
select p.cid cid,p.uid,count(*) cishu
from play_record_tb p
group by cid,uid
having count(*)>1
) a
left join course_info_tb c on c.cid=a.cid
group by a.cid
order by sum(a.cishu) desc
limit 3
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