title: date_sub ok with mysql, ko with postgresql
body: <p>This query which works with mySQL doesn't work with Postgresql:</p>
  
  <pre><code>select ... from ... where (id = ... and ( h &gt; date_sub(now(), INTERVAL 30 MINUTE)))  
  </code></pre>
  
  <p>The error is:</p>
  
  <pre><code>Query failed: ERREUR:  erreur de syntaxe sur ou près de « 30 »  
  </code></pre>
  
  <p>Any ideas ?</p>