MySQL: Display one random result which a user has not voted on
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I need help on displaying one random result in which the current user has not voted on.

Currently my database setup and the last query I have tried can be found on http://sqlfiddle.com/#!2/2f91b/1

Basically I can isolate each individual item using this query:

    SELECT a.img_url, a.item_id, a.user_id, a.img_status, b.item_question, c.user_name, c.user_fbid, d.voter_id, count(d.img_id) AS totalVotes
    FROM os_photos a 
    LEFT JOIN os_items b ON a.item_id = b.item_id
    LEFT JOIN os_users c ON a.user_id = c.user_id
    LEFT JOIN os_votes d ON a.img_id = d.img_id
    GROUP BY a.img_id
    ORDER BY RAND()
    LIMIT 1

My Problem is: With the SQL knowledge that I have, I am unable to isolate the results to show only the rows in which user #2 has not voted on.  I realize the problem is when I use group by, it combines the voter_id and therefore I am unable to check if user #2 has had any input for the item.

Your help, advise and knowledge is greatly appreciated.