Drill 24: Why this way — Database design basics

CREATE TABLE authors (
  id SERIAL PRIMARY KEY,
  name TEXT NOT NULL
);

CREATE TABLE books (
  id SERIAL PRIMARY KEY,
  title TEXT NOT NULL,
  author_id INTEGER NOT NULL REFERENCES authors(id)
);

CREATE TABLE tags (
  id SERIAL PRIMARY KEY,
  label TEXT NOT NULL UNIQUE
);

CREATE TABLE book_tags (
  book_id INTEGER NOT NULL REFERENCES books(id),
  tag_id INTEGER NOT NULL REFERENCES tags(id),
  PRIMARY KEY (book_id, tag_id)
);