Скалярный подзапрос с помощью QueryBuilder

SELECT `id`, `shop_group_id`, `name`, `price`,

(SELECT `value` FROM property_value_ints WHERE property_value_ints.entity_id = `shop_items`.id AND property_value_ints.property_id = 45 LIMIT 1) AS old_price,
(SELECT `value` FROM property_value_ints WHERE property_value_ints.entity_id = `shop_items`.id AND property_value_ints.property_id = 53 LIMIT 1) AS old_price_curr,
(SELECT `value` FROM list_items WHERE list_items.id = old_price_curr AND list_items.list_id = 28 LIMIT 1) AS old_price_curr_val,
(SELECT `exchange_rate` FROM shop_currencies WHERE shop_currencies.code = old_price_curr_val) AS old_price_curr_coef

FROM `shop_items`
ORDER BY old_price DESC

$oCore_QueryBuilder_Select = Core_QueryBuilder::select(array('(SELECT `value` FROM property_value_ints WHERE property_value_ints.entity_id = `shop_items`.id AND property_value_ints.property_id = 45 LIMIT 1)', 'old_price'))->from('shop_items');

    // SELECT (SELECT MAX(`column2`) FROM `t2`) FROM `t1`
    $oCore_QueryBuilder_Select2 = Core_QueryBuilder::select('MAX(column2)')->from('t2');
    $oCore_QueryBuilder_Select = Core_QueryBuilder::select($oCore_QueryBuilder_Select2)->from('t1');

$oCore_QueryBuilder_Select2 = Core_QueryBuilder::select( ....;
$oCore_QueryBuilder_Select = Core_QueryBuilder::select(array($oCore_QueryBuilder_Select2, 'old_price'))->from('shop_items');

$oCore_QueryBuilder_Select2 = Core_QueryBuilder::select('value')
                    ->where('property_id', '=', 13)
                    ->where('entity_id', '=', Core_QueryBuilder::expression('`shop_items`.`id`'))
                    ->from('property_value_floats')
                    ->limit(1);
$oCore_QueryBuilder_Select3 = Core_QueryBuilder::select('value')
                    ->where('property_id', '=', 14)
                    ->where('entity_id', '=', Core_QueryBuilder::expression('`shop_items`.`id`'))
                    ->from('property_value_ints')
                    ->limit(1);
$Shop_Controller_Show
                    ->shopItems()
                    ->queryBuilder()
                    ->select(array($oCore_QueryBuilder_Select2, 'ling'))
                    ->select(array($oCore_QueryBuilder_Select3, 'veg'))

class Shop_Item_Observer
{
   static public function onBeforeGetXml($object, $args)
   {
      // Добавить новый тег, равный price * 2
      $object->addXmlTag('myTag', $object->price * 2);
   }
}

// Add shop_item observer
Core_Event::attach('shop_item.onBeforeGetXml', array('Shop_Item_Observer', 'onBeforeGetXml'));