将Magento PHP查询限制为持续30分钟

Question

我已经尝试过滤这么多方式而且我被困住了任何帮助表示赞赏。 updated_at出现： 2014-08-29 16:59:43

目前收到错误： 在/chroot/home/campdev/dev8.campsaver.com/html/lib/Zend/Db/Statement/Pdo.php:228中，DATEADD不存在

    $res = Mage::getSingleton('core/resource'); $ordersTable = $res->getTableName('sales/order');
    $db = $res->getConnection('sales_read'); 
    $lastEntityId = 0; $sql = new Varien_Db_Select($db);
    if ($lastOrder) { $lastEntityId = self::getOrderEntityId($db, $sql, $lastDate, $lastOrder); }
    $sql = $db->select()
              ->from($ordersTable, 'entity_id')
              ->where('store_id=?', self::$_storeId, Zend_Db::INT_TYPE)
              ->where('updated_at < DATEADD(minute, -, GETDATE())')
              ->where("entity_id > $lastEntityId")
              ->limit($batchsize, $startnum);
    if (self::$_debug) { echo "Executing SQL: $sql\r\n"; }
    $ordRows = $db->fetchAll($sql);