- this tables includes all books we use in our project
- this tables contains all users that logen into the database
- referenced by 2 tables (saved_books, book_collections) for user_id
- this tables contains all saved books by user
- we retieve books for specific user using specified the user_id of current user that loged into the database and the collection_id where the book saved in
- references to 3 tables (saved_books, book_collections, amazon_books)
- reference properties are for book_id in amazon_books, user_id in users and collection_id in book_collections table
- finally this one contains all collections of user
- a collection contains many books
- reference to only user_id in users table
