title: Yii: Select 20 last entries order by id ASC
body: <p>I would like to get the 20 last entries of my table but order by ascending id.</p>
  
  <p>In Sql it's not very complicated:</p>
  
  <pre><code>SELECT * 
  FROM (SELECT * FROM comments
        WHERE postID='$id' 
        ORDER BY id DESC 
        LIMIT 20) t
  ORDER BY id ASC;
  </code></pre>
  
  <p>But I would like to to it with my yii model like:</p>
  
  <pre><code>Comment::model()-&gt;findAll($criteria)
  </code></pre>
  
  <p>But i really don't know what I should put in my CDbCriteria!</p>