您需要为集合的select对象添加一个连接。在本例中，这非常简单，因为所涉及的两个表（sales_flat_order_grid和sales_flat_order）可以很容易地通过两个表共有的entity_id列进行链接：

$collection = Mage::getResourceModel('sales/order_grid_collection');
$select = $collection->getSelect();
$resource = Mage::getSingleton('core/resource');

$select->join(
    array('order' => $resource->getTableName('sales/order')),
    'main_table.entity_id = order.entity_id',
    array('state')
);