CREATE TABLE `news_articles` (
  `news_articles_id` int(11) NOT NULL auto_increment,
  `news_articles_titre` varchar(256) NOT NULL,
  `news_articles_contenu` text NOT NULL,
  `news_articles_auteur` varchar(30) NOT NULL default 'leo48',
  `news_articles_date` datetime NOT NULL,
  PRIMARY KEY  (`news_articles_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ;

CREATE TABLE `news_commentaires` (
  `news_commentaires_id` int(11) NOT NULL auto_increment,
  `news_articles_id` int(11) NOT NULL,
  `news_commentaires_message` text NOT NULL,
  `news_commentaires_auteur` varchar(30) NOT NULL,
  `news_commentaires_date` datetime NOT NULL,
  PRIMARY KEY  (`news_commentaires_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;

<?php
//Connexion BDD ....

$req = $bdd->query('SELECT news_articles_id AS news_id,
                        news_articles_titre AS news_titre, 
                        news_articles_contenu AS news_contenu,
                        news_articles_auteur AS news_auteur,
                        DATE_FORMAT(news_articles_date, \'%d/%m/%Y à %Hh%imin%ss\') AS news_date,
                        FROM news_articles ORDER BY news_articles_date DESC LIMIT 0,5') or exit(print_r($bdd->errorInfo()));
while($data1 = $req->fetch()) {

$req1 = $bdd->prepare('SELECT COUNT(*) AS nb_coms FROM news_commentaires WHERE news_id = :news_id');
$req1->bindValue(':news_id', $data1['news_id'], PDO::PARAM_INT);
$req1->execute()
$data2 = $req1->fetch();

// Suite du code.

Mon problème

SELECT n.news_articles_id news_id, 
       n.news_articles_titre news_titre,
       n.news_articles_contenu news_contenu,
       n.news_articles_auteur news_auteur, 
       DATE_FORMAT(n.news_articles_date, '%d/%m/%Y à %Hh%imin%ss') news_date,  
      (COUNT(com.news_commentaires_id) nb_coms WHERE com.id_news = :id_news)
FROM news_articles n
RIGHT JOIN commentaires com
ON n.news_articles_id = com.news_articles_id
ORDER BY n.news_articles_date DESC LIMIT 0,5

SELECT N.news_articles_id,
       N.news_articles_titre,
       N.news_articles_contenu,
       N.news_articles_auteur,
       DATE_FORMAT(n.news_articles_date, '%d/%m/%Y à %Hh%imin%ss') AS news_date,
       COUNT(C.*) AS nb_coms
FROM news_articles N
LEFT OUTER JOIN commentaires C
    ON N.news_articles_id = C.news_articles_id
GROUP BY N.news_articles_id,
       N.news_articles_titre,
       N.news_articles_contenu,
       N.news_articles_auteur,
       news_date
ORDER BY N.news_article_date DESC
LIMIT 5;