Hi all - I'm designing a library management system for a department at my university and I wanted to enlist your eyes on my proposed schema. This post is primarily concerned with how we store multiple copies of each book; something about what I've designed rubs me the wrong way, and I'm hoping you all can point out better ways to tackle things.

For dealing with users checking out books, I've devised three tables: book, customer, and book_copy. The relationships between these tables are as follows:

• Every book has many book_copies (to avoid duplicating the book's information while storing the fact that we have multiple copies of that book).
• Every user has many book_copies (the other end of the relationship)

The tables themselves are designed like this:

------------------------------------------------
book
------------------------------------------------
+ id
+ title
+ author
+ isbn
+ etc.
------------------------------------------------

------------------------------------------------
customer
------------------------------------------------
+ id
+ first_name
+ first_name
+ email
+ address
+ city
+ state
+ zip
+ etc.
------------------------------------------------

------------------------------------------------
book_copy
------------------------------------------------
+ id
+ book_id (FK to book)
+ customer_id (FK to customer)
+ checked_out
+ due_date
+ etc.
------------------------------------------------

Something about this seems incorrect (or at least inefficient to me) - the perfectionist in me feels like I'm not normalizing this data correctly. What say ye? Is there a better, more effective way to design this schema?

Thanks!