Question

I have oracle tables like below:

User - UserId,
Item - ItemId,
UserVote - UserVoteId, UserId, ItemId. 

Now a user can vote multiple times. I am having a hard time with this query: Get item(s) most voted uniquely – meaning multiple votes from the same person count only as one.

If it was SQL Server, I might have created temp table and all, but I do not know how to handle in Oracle. I’m also having a hard time thinking how to handle tie, meaning if two items both have 18 “unique” votes. I would want both items in that case.

Answer 1

select ItemID,
       VoteCount
from
  (
    select ItemID,
           count(distinct UserId) as VoteCount,
           rank() over(order by count(distinct UserId) desc) as rn
    from UserVote
    group by ItemID
  ) U
where rn = 1;