Peab olema kirjeldatud raamatukogu mudel. On 3 üksust: "Autor", "Raamat", "Lugeja". Füüsiliselt on ainult üks raamat ja see võib kuuluda ainult ühele lugejale. Tuleb koostada tabelid raamatukoguks, et seda arvesse võtta.

To describe the library model with entities "Author", "Book", "Reader" and the condition that each book is physically unique and can only be with one reader at a time, the following tables can be used:

1. Author

• id (PK)
• name

2. Book

• id (PK)
• title
• author_id (FK to Author.id)
• reader_id (FK to Reader.id, nullable)

3. Reader

• id (PK)
• name

Explanation:

• Each book is linked to an author via author_id.
• The reader_id field in the book table indicates which reader currently has the book. If the book is not loaned out, this field will be NULL.

This ensures that each book exists in a single copy and can only be with one reader at a time.