text: SELECT title, 'Book' AS Item
  FROM book
  LEFT JOIN checkout_item ON checkout_item.book_id = book.id
  WHERE checkout_item.member_id IS NULL
  UNION
  SELECT title, 'Movie'
  FROM movie
  LEFT JOIN checkout_item ON checkout_item.movie_id = movie.id
  WHERE checkout_item.member_id IS NULL
  ORDER BY Item