public function fetch($query, $parameters = array())
    {
        try {
            $sth = $this->query($query, $parameters);
            if ($sth === false) {
                return false;
            }
            return $sth->fetch(PDO::FETCH_ASSOC);
        } catch (PDOException $e) {
            throw new DbException("Error query: " . $e->getMessage());
        }
    }