title: magento grid cannot find the column when I filter
body: <p>I have a custom module that has it's own grid.  One of the fields that I pull into the grid is a count of records (notes) that are associated with the entry.  It works fine and shows the count in the grid, it sorts fine too, but when I filter I get a message saying it cannot find the column.  </p>
  
  <p>Here is the error:</p>
  
  <pre><code>SQLSTATE[42S22]: Column not found: 1054 Unknown column 'note_count' in 'where clause'
  </code></pre>
  
  <p>And here is the code</p>
  
  <pre><code>class Ssi_Crm_Model_Mysql4_Quote_Collection extends Mage_Core_Model_Mysql4_Collection_Abstract
  {
  
      protected function _construct()
      {
          $this-&gt;_init('crm/quote');
      }
  
      protected function _initSelect()
      {
          parent::_initSelect();
          $this-&gt;_joinUserSet();
          return $this;
      }
  
      protected function _joinUserSet()
      {
          $this-&gt;getSelect()
           -&gt;columns("(SELECT COUNT(note) FROM mage_crm_notes WHERE entity_id = main_table.quote_id AND entity_type = 'quote') as note_count")
              -&gt;join(
                  array('user'=&gt;$this-&gt;getTable('admin/user')),
                  'main_table.user_id=user.user_id',
                  array('username' =&gt; 'user.username', 'email' =&gt; 'user.email'));
  
  
          return $this;
  
      }
  </code></pre>