public function defaultDatabase($which_connection='')
    {
        $which_connection = $which_connection === '' ? $this->default_db : $which_connection;
        $adapter = $this->getAdapter($this->connectionType($which_connection));
        if ($which_connection == '') {
            $which_connection=$this->default_db;
        }

        if (count($this->connections) == 0) {
            return false;
        }

        $query = $adapter->defaultDatabase();

        $ret = false;
        $try = $this->query($query, $which_connection);
        if ($try && $this->num_rows($try) > 0) {
            $row = $this->fetch_row($try);
            $ret = $row['dbname'];
        }

        return $ret;
    }