Mine

create table Tguestbooks ( 
 		id                              serial primary key,
		name				varchar(264) not null unique,
		user_id				integer not null,
		date_cr                         timestamp default now() not null,
		moderation			integer not null,
		foreign key                     (user_id) references Tusers
};

create table Tguestbook_message (
		id                              serial primary key,
		guestbooks_id			integer not null,
		user_id				integer not null,
		question			text,
		answer				text,
		foreign key                     (user_id) references Tusers
		foreign key                     (unit_id) references Tguestbooks
);