title: How to join collections in Magento?
body: <p>I am trying to join a custom collection with products to show the product name (not just the id) in the admin grid widget. So far i can't find the correct syntax.</p>
  
  <p>I am able to retrieve the products with the product name by the following:</p>
  
  <blockquote>
    <p>Mage::getModel('catalog/product')->getCollection()->addAttributeToSelect('name'); </p>
  </blockquote>
  
  <p>and i can retrieve my custom collection with:</p>
  
  <blockquote>
    <p>Mage::getResourceModel('xyz_mymodule/model_collection');</p>
  </blockquote>
  
  <p>How do i join the two so that the module collection is the primary collection and the id as returned by $model->getId() is still the id of my custom collection?</p>