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 Tguestbooks_message (		id                              serial primary key,		guestbook_id			integer not null,		user_question_id		integer not null,		user_answer_id			integer,		question			text,		answer				text,		date_question                   timestamp default now() not null,		date_answer			timestamp,		foreign key                     (user_id) references Tusers		foreign key                     (unit_id) references Tguestbooks);