Can BookID and AuthorID be the same number? That doesn't seem prudent.
Can BookID and AuthorID be the same number? That doesn't seem prudent.
There's nothing necessarily wrong or unusual about a BookID potentially having the same value as one of the AuthorID's as these are two unrelated Primary Key values. The relationship in this case would usually be a many-to-many model, using a junction table. The junction table is what controls the relationship.
I don't see how they can and have meaning, but consider.
What is a Book? How is a Book distinguished form all other Books in your database? Probably by a Primary Key where, the PrimaryKey value identifies uniquely each record in your table. So a Book record in the tblBook with PK value 1 could represent title "Database Intro". That is BookID = 1 represents "Database Intro".
What exactly is an Author? How is an Author distinguished from all other Authors in your database? As above
So an Author record in the tblAuthor with PK value 1 could represent title "John Kensington". So AuthorID =1 represents "John Kensington"Probably by a Primary Key where, the PrimaryKey value identifies uniquely each record in your table.
So even though the Book entitled "Database Intro" is identified with PK value 1 (BookID =1), and Author named "John Kensington" is identified with PK value 1 (AuthorID = 1) -they both have value 1, they represent different objects/things (Book vs Author). So the values could be equal, but it has no meaning in this context.
See this link for info on several articles related to database design and planning.
Good luck and sorry for being so long-winded.
Update: I see Sean has responded---I agree with his post
Thanks to all who responded. I appreciate the help and additional resource.