CREATE TABLE people (
	id_people SERIAL PRIMARY KEY,
	name text
);
CREATE TABLE author (
	id_author SERIAL PRIMARY KEY,
	ref_people int4
);
CREATE TABLE user (
	id_user SERIAL PRIMARY KEY,
	ref_people int4,
	expiration date DEFAULT 'now'
);
CREATE TABLE book (
	id_book SERIAL PRIMARY KEY,
	title text,
	author text,
	ref_user int4,
	date date DEFAULT 'now'
);
CREATE TABLE manager (
	id_manager SERIAL PRIMARY KEY,
	password text,
	ref_people int4
);
CREATE TABLE write (
	id_write SERIAL PRIMARY KEY,
	ref_book int4,
	ref_author int4
);