public static function getAllReservedWords() {
        global $CFG;

        $generators = array('mysql', 'postgres', 'oracle', 'mssql');
        $reserved_words = array();

        foreach($generators as $generator) {
            $class = $generator . '_sql_generator';
            require_once("$CFG->libdir/ddl/$class.php");
            foreach (call_user_func(array($class, 'getReservedWords')) as $word) {
                $reserved_words[$word][] = $generator;
            }
        }
        ksort($reserved_words);
        return $reserved_words;
    }