public static function GetInstanceFromSystemName($sSystemName)
    {
        $sQuery = "SELECT * FROM `pkg_shop_rating_service` WHERE `system_name` = '".MySqlLegacySupport::getInstance()->real_escape_string($sSystemName)."'";
        $aData = MySqlLegacySupport::getInstance()->fetch_assoc(MySqlLegacySupport::getInstance()->query($sQuery));
        if (is_array($aData)) {
            $oInstance = TdbPkgShopRatingService::GetNewInstance($aData); // need to do this to morph to the correct subclass
        } else {
            $oInstance = null;
        }

        return $oInstance;
    }