produit aleatoire pour liste categorie

$db =& JFactory::getDBO();
$q = "SELECT CONCAT(p.product_genre , '. ', p.product_description) AS alt  ,f.file_path AS image FROM #__hikashop_file f  
INNER JOIN #__hikashop_product_category c  ON f.file_ref_id  =  c.product_id  
INNER JOIN  #__hikashop_product p ON p. product_id =  c.product_id WHERE f.file_ordering= 0  AND c.category_id= ".$this->row->category_id." ORDER BY RAND() LIMIT 0,1;";
$db->setQuery($q);
$r = $db->loadObject();
$img = $this->image->uploadFolder_url .'/' . $r->image;
$alt = $r->alt;