Smarter way to add fields to order grid.

gistfile1.php

<?php

/*
  Summoned with:
  <config>
    <global>
      <events>
        <sales_order_resource_init_virtual_grid_columns>
            <observers>
              <capture_order_grid_fields>
                <class>Company_Module_Model_Observer</class>
                <method>captureOrderGridFields</method>
              </capture_order_grid_fields>
            </observers>
        </sales_order_resource_init_virtual_grid_columns>
      </events>
      ...
    </global>
  </config> */
  
  class Company_Module_Model_Observer{


    // only runs when saving or updating a single order record.
    public function captureOrderGridFields($observer){
        $event = $observer->getEvent();
        $resource = $event->getResource();

        $adapter       = $resource->getReadConnection();
        $concatCityState = $adapter->getConcatSql(array('{{table}}.city', $adapter->quote(', '), '{{table}}.region'));
        $resource->addVirtualGridColumn(
                'shipping_city_state',
                'sales/order_address',
                array('shipping_address_id' => 'entity_id'),
                $concatCityState
            );
    }
    
  }