function using($columns)
    {
        $lastJoin = $this->getLastJoinSource();

        if (null === $columns) {
            $lastJoin->right = null;
            return $this;
        }

        $columns = is_array($columns) ? $columns : func_get_args();

        if ($lastJoin->right instanceof Using) {
            $lastJoin->right->expression = array_merge(
                $lastJoin->right->expression,
                $columns
            );
        } else {
            $lastJoin->right = new Grouping($columns);
        }
        return $this;
    }