title: Cakephp Find operation unknown field error
body: <p>I have 2 tables</p>
  
  <p>A Prison table and a Warden table.
  A Prison can have several Wardens scheduled to work for the prison.
  Warden records have start date and end date fields the time range that they will work for a Prison.</p>
  
  <p>I have set up an association, which is Prison hasMany Warden.
  Warden table has a foreign key field prison_id.</p>
  
  <p>If i do a $this->Warden->find('all');</p>
  
  <p>I will get all Prisons, with all their Wardens scheduled for the past and future.</p>
  
  <p>I only want to get Wardens working for a Prison for a particular date.</p>
  
  <p>I'm trying to do something like</p>
  
  <pre><code>    $searchfilter = array(
                          'Warden.startdate &lt;=' =&gt; $date,
                          'Warden.enddate   &gt;=' =&gt; $date,
                          );        
  
      return $this-&gt;Prison-&gt;find('all', array('conditions' =&gt; $searchfilter));
  </code></pre>
  
  <p>But this results in unknown field error.</p>