title: CakePHP: Find where field is not null
body: <p>I need to select all rows where <code>User.site_url</code> is not null. It's simple enough to do this in a regular <strong>MySQL</strong> query but how is this done in <strong>CakePHP</strong>?</p>
  <p>The manual mentions the following:</p>
  <pre><code>array (&quot;not&quot; =&gt; array (
          &quot;Post.title&quot; =&gt; null
      )
  )
  </code></pre>
  <p>I have tried the following but it's still returning everything</p>
  <pre><code>$this-&gt;User-&gt;find('all', array('conditions' =&gt; array('not' =&gt; array('User.site_url'))));
  </code></pre>