create table t_class (
	class_id		integer auto_increment primary key not null,
	parent_id		integer null references t_class(class_id), 
	class			varchar(64) not null,
	fertile			char(1) not null,
	final			char(1) not null,

	index (class_id),
	unique (class_id),

	index (parent_id),

	index (class),
	unique (class)
);