Question

This is a more detailed question as my previous attempt wasn’t clear enough. I’m new to MySQL and have no idea about the best way to do certain things. I’m building a voting application for images and am having trouble with some of the finer points of MySQL

My db

_votes

• id
• voter_id
• image_id

_images

• id
• file_name
• entrant_id
• approved

_users

• id
• …

Basically I need to do the following:

1. tally up all votes that are approved
2. return the top 5 with the most votes
3. check if the user has voted on each of these 5 (return Boolean) from another table

I’ve tried variations of

SELECT i.id, i.file_name, i.total_votes
FROM _images i WHERE i.approved = 1 
CASE WHEN (SELECT count(*) from _votes v WHERE v.image_id = i.id AND v.voter_id = ?) > 0 THEN '1' ELSE '0' END 'hasvoted'
ORDER BY i.total_votes DESC LIMIT ".($page*5).", 5

is that something I should try and do all in one query?

This query was working fine before I tried to add in the ‘hasvoted’ boolean:

SELECT id, file_name, total_votes FROM _images WHERE approved = 1 ORDER BY total_votes DESC LIMIT ".($page*5).", 5

At the moment I’m also storing the vote count in the _images table and I know this is wrong, but I have no idea about how to tally the votes by image_id and then order them.

Answer 1

Let me give this a shot to see if I understand your question:

SELECT i.*,(SELECT COUNT(*) FROM _votes WHERE i.id = image_id) AS total_votes, (SELECT count(*) from _votes where i.id = image_id and user_id = ?) as voted  FROM _images AS i WHERE i.approved = 1