title: Silverstripe: DataList Filter equivalent of 'Value > x OR Value = y'
body: <p>I understand that I can specify multiple values for my filter in a way such as:</p>
  
  <pre><code>xxx::get()-&gt;filter('FirstName', array('Sam', 'Sig'));
  </code></pre>
  
  <p>Which gives me the equivalent of:</p>
  
  <pre><code>... WHERE FirstName = 'Sam' OR FirstName = 'Sig'
  </code></pre>
  
  <p>However, there doesn't appear to be anyway of combining <code>OR</code>'s with the modifiers (<code>'LastVisited:GreaterThan' =&gt; '2011-01-01'</code>)</p>
  
  <p>I need to be able to filter like so:</p>
  
  <pre><code>WHERE ExpiryDate &gt; 29-11-2012 OR ExpiryDate IS NULL
  </code></pre>
  
  <p>Is what I am trying to achieve possible? I have read the docs but have not found the answer to my issue.</p>
  
  <p>Thanks</p>