How to assign result of $this->_select query to a variable

[oowwaa]

Hello, i have a $this->_select  statement in my AdminOrdersController.php override, which add a column "Address tester"

$this->_select .= ', 
address.`address1` as saddress,
a.id_order as id_trackingField,
a.id_order as id_manageBtns,
a.id_order as id_addressField,
CONCAT(
address.`firstname`," ", address.`lastname`, "\n", 
address.`address1`, \' \', 
address.`address2`, \' \', 
address.`postcode`," ", address.`city`, \' \', 
country_lang.`name`,\' \'
) as sAddressFull
';

$this->fields_list['sAddressFull'] = array(
'title' => $this->l('Address tester')
);

It adds the correct address data in the "Address tester" column, however i need this data (sAddressFull) to be assigned to a variable instead, how to achieve this?

        $sql = new DbQuery();
        $sql->from('order');
		$sql->_select .= ', 
		address.`address1` as saddress,
		CONCAT(
		address.`firstname`," ", address.`lastname`, "\n", 
		address.`address1`, \' \', 
		address.`address2`, \' \', 
		address.`postcode`," ", address.`city`, \' \', 
		country_lang.`name`,\' \'
		) as sAddressFull
		';

        $customVal = Db::getInstance()->getValue($sql);         
        //$customVal =  Db::getInstance(_PS_USE_SQL_SLAVE_)->executeS($sql);

        $this->context->smarty->assign('fullAddress',print_r ($customVal));

All my other attempts failed as well.

Edited May 8, 2017 by oowwaa (see edit history)