title: Filtering a joined column
body: <p>I am creating a stock report in the admin and have everything working so far, except that I can't seem to be able to filter on the joined column.</p>
  
  <p>I have joined the stock information, using the following to grab my collection.</p>
  
  <pre><code>$collection = Mage::getModel('catalog/product')-&gt;getCollection()
                  -&gt;addAttributeToSelect('name')
                  -&gt;addAttributeToSelect('sku')
                  -&gt;addAttributeToSelect('price')
                  -&gt;setStoreId($storeId);
  $collection-&gt;addFieldToFilter('type_id', 'simple');
  
  // Add on the stock qty information
  $collection-&gt;getSelect()-&gt;join( array('stock'=&gt;'ccmg_cataloginventory_stock_item'), 'e.entity_id = stock.item_id', array('stock.qty'));
  </code></pre>
  
  <p>This is causing it to display, but you can't filter or sort the column. I assume because the options aren't being passed back into the join. However, the other columns can be sorted and filtered and the matching data is pulled back and displayed. </p>
  
  <p>I've been searching but most posts are on the Magento forums from 2008, and I'm using 1.6! Any pointers would be great!</p>