Question

I have a database with multiple content types and users, as well as a separate database with likes. I’m trying to figure out which users have received the most likes for any of their content, no matter what the type.

I’ve been able to figure out queries for finding the most liked users by specific content types, but going with any content type is proving to be a bit more difficult.

It might be worth noting that there are millions of records in this database.

Here’s the work I’ve been doing on creating a query… I’m pretty sure it’s not correct!

SELECT picture.user_id, video.creator_id, post.author_id
FROM likes_service.likes
INNER JOIN prod.pictures picture ON likes.obj_id = picture.id
INNER JOIN prod.videos video ON likes.obj_id = video.id
INNER JOIN prod.posts post ON likes.obj_id = post.id
GROUP BY picture.user_id, video.creator_id, post.author_id
ORDER BY COUNT(picture.user_id), COUNT(video.creator_id), COUNT(post.author_id) DESC
LIMIT 20;

Could anybody please give me a hint or point me in the right direction? I feel like I’m getting close…

Thanks!

Answer 1

I think you want a UNION, not a multi-way JOIN.

select objects.user_id user_id, sum(likes.like_count) like_count
from (
    select user_id, id
    from prod.pictures
    union all
    select creator_id, id
    from prod.videos
    union all
    select author_id, id
    from prod.posts) objects
join (select obj_id, count(*) likes_count
      from likes_service.likes
      group by obj_id) likes on likes.obj_id = objects.id
group by user_id
order by like_count desc