I have this SQL, yet it returns an error: Invalid use of group function. Any ideas why?
<?php
$sql = "SELECT i.image_id, TRUNCATE(SUM(r.rating) / COUNT(*), 2) AS realrating
FROM images i, rating r
WHERE (i.category_id = '$currCat') AND (i.image_id = r.image_id)
AND (TRUNCATE(SUM(r.rating)/COUNT(*), 2) < '$currRanking')
AND (i.validated = '1') GROUP BY i.image_id LIMIT 1";
$result = mysql_query($sql);
$row = mysql_fetch_assoc($result);
?>
MySQL error: Invalid use of group function... help!
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