SQL Request on multiple tables - mysql

Question

I've put some information in this SQL Fiddle : http://www.sqlfiddle.com/#!2/0745c0/4/0
You'll see table structure and my request.
SELECT
cov.id AS cov_id,
cov.utilisateurs_uid AS cov_uid,
cov.timestamp_created as timestamp,
cov.invisible as invisible,
COALESCE(numreports, 0) AS numreports
FROM
cforge_covers AS cov
LEFT OUTER JOIN cforge_votes AS vot ON cov.id = vot.covers_id AND vot.utilisateurs_uid != 123456789
LEFT JOIN (SELECT rep.covers_id,
COUNT(rep.id) AS numreports
FROM cforge_reports AS rep
GROUP BY rep.covers_id) reports ON reports.covers_id = cov.id
WHERE invisible=0 AND (numreports < 2 OR numreports IS null OR valide > 0) AND cov.timestamp_created > '1370815140' AND cov.timestamp_created < '1373493540' GROUP BY cov.id
ORDER BY rand() DESC LIMIT 0,2
When a user creates a picture, a line is created in cforge_covers, with his Facebook UID, ID of the picture and a timestamp.
Cover pictures can be voted, once per user, and the votes ares stored in cforge_votes, where you can have the same covers_id multiple times and utilisateurs_uid (users_id) only once per covers_id max.
Cover pictures can also be reported on the same basis as votes : once per user.
The purpose of my request is to fetch :
two random covers
which haven't been reported or moderated (values stored in cforge_reports)
for which the user hasn't already voted
The last part is causing my problem : I try to exclude a specific utilisateurs_uid but as many users vote for an image, other votes for the cover make it valid to show even if the user has already voted for it.
How can I write this request better ?
Thanks in advance for your time !

Answer 1

You want to make use of WHERE NOT EXISTS rather than LEFT JOIN. It is unclear if you want an item that has never been moderatred, or one that has been moderated once or none (your requirements and code say different things). If you truly want one that has never been moderated, then try NOT EXISTS in both cases.
Also, I would suggest that you be diligent about formatting and aliasing All The Things. It will help those reading your code and even you, when you go back to look at it later.
SELECT cov.id AS cov_id
,cov.utilisateurs_uid AS cov_uid
,cov.timestamp_created as timestamp
,cov.invisible as invisible
,COALESCE(reports.numreports, 0) AS numreports
FROM cforge_covers AS cov
LEFT JOIN (SELECT rep.covers_id,
COUNT(rep.id) AS numreports
FROM cforge_reports AS rep
GROUP BY rep.covers_id) reports ON reports.covers_id = cov.id
WHERE cov.invisible=0
AND (reports.numreports < 2
OR reports.numreports IS null
OR ????.valide > 0)
AND cov.timestamp_created > '1370815140'
AND cov.timestamp_created < '1373493540'
AND NOT EXISTS ( SELECT 1 FROM cforge_votes vot WHERE cov.id = vot.covers_id AND vot.utilisateurs_uid = 123456789)
ORDER BY RAND() DESC LIMIT 0,2