private function _getColumns($table)
    {
        if (isset($this->_tables[$table])) {
            return $this->_tables[$table];
        };
        $this->_tables[$table] = false;
        if ($rows = $this->selectArray("PRAGMA table_info({$table})")) {
            $cols = array();
            foreach ($rows as $row) {
                $cols[] = $row['name'];
            };
            if (count($cols) > 0) {
                $this->_tables[$table] = $cols;
            };
        };
        return $this->_tables[$table];
    }