title: CakePHP LEFT JOIN sorting issue
body: <p>I'm using cakePhp 2.x version and following is my view and controller for a datagrid, I want Area and Boxes both to be sorted by user. Box can be sorted, but Area first sorting is working, after that when click on sorting, page is refreshed but it doesn't sort. What could be the reason?</p>
  <pre class="lang-php prettyprint-override"><code>&lt;table class=&quot;index&quot;&gt;
  &lt;thead&gt;
      &lt;tr&gt;
          &lt;th&gt;&lt;?php echo $this-&gt;Paginator-&gt;sort('A.title', 'Area')?&gt;&lt;/th&gt;
          &lt;th&gt;&lt;?php echo $this-&gt;Paginator-&gt;sort('B.title', 'Boxes')?&gt;&lt;/th&gt;
          &lt;th&gt;Internal&lt;/th&gt;
          &lt;th&gt;External&lt;/th&gt;
      &lt;/tr&gt;
  &lt;/thead&gt;
  </code></pre>
  <pre class="lang-php prettyprint-override"><code>$this-&gt;paginate['contain'] = array();
  $this-&gt;paginate['joins'] = array(
      array(
          'table' =&gt; 'a_table',
          'alias' =&gt; 'A',
          'type' =&gt; 'LEFT',
          'conditions' =&gt; array(
              'A.key = B.id',
              'A.status' =&gt; 'Active'
          )
      )
  );
  
  $conditions = array();
  $this-&gt;paginate['fields'] = array('B.*', 'A.title');
  $this-&gt;paginate['order'] = array('A.title', 'B.title');
  
  if(!empty($this-&gt;request-&gt;data['SignalBox']))
  {
      if($this-&gt;request-&gt;data['SignalBox']['box'])
          $conditions['B.title LIKE'] = '%'.$this-&gt;request-&gt;data['SignalBox']['box'].'%';
  
      if($this-&gt;request-&gt;data['SignalBox']['area'])
          $conditions['A.title'] = $this-&gt;request-&gt;data['SignalBox']['area'];
  }
  
  if($conditions)
      $this-&gt;paginate['conditions'] = $conditions;
  
  $data = $this-&gt;paginate('B');
  
  $this-&gt;set('data', $data);
  </code></pre>