text: CREATE TABLE type (
  	id SERIAL PRIMARY KEY,
  	name VARCHAR(20) NOT NULL
  );
  
  CREATE TABLE product (
  	id SERIAL PRIMARY KEY,
  	name VARCHAR(50) NOT NULL UNIQUE,
  	type_id INTEGER REFERENCES type (id),
  	expired_date TIMESTAMP, 
  	price DOUBLE PRECISION,
  	num INTEGER NOT NULL
  );