Example SQL Relationship

example1.sql

CREATE TABLE books (
  id serial,
  title varchar(100) NOT NULL,
  author varchar(100) NOT NULL,
  published_date timestamp NOT NULL,
  isbn char(12),
  PRIMARY KEY (id),
  UNIQUE (isbn)
);

CREATE TABLE reviews (
  id serial,
  book_id integer NOT NULL,
  reviewer_name varchar(255),
  content varchar(255),
  rating integer,
  published_date timestamp DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (id),
  FOREIGN KEY (book_id) REFERENCES books(id)
);

example2.sql

CREATE TABLE books (
  id serial,
  title varchar(100) NOT NULL,
  author varchar(100) NOT NULL,
  published_date timestamp NOT NULL,
  isbn char(12),
  PRIMARY KEY (id),
  UNIQUE (isbn)
);

CREATE TABLE reviews (
  id serial,
  book_id integer REFERENCES books(id),
  reviewer_name varchar(255),
  content varchar(255),
  rating integer,
  published_date timestamp DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (id)
);