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databasedatabase-normalizationfunctional-dependencies3nf

Is table `Books` with two unique columns `isbn` (id of book) and `title` that depend on each other in 3NF?

Table Books has two columns, isbn (id of book) and title.

They are unique and they depend on each other.

Is it 3NF?

3NF requires every non-key attribute to depend on the key.

Solution

  • Because you say "Both of them are unique and they depend on each other", you have 2 keys (each consisting of a single attribute) and there no non-prime attributes at all. Hence your schema is in 3NF.

    In addition, you might want to reconsider the claim that "ISBN" could reasonably be functionally dependent on "book title". The book titled "Introduction to database systems" (a classic in the field) has had 8 different editions, and I'm pretty certain those editions all have a different ISBN, while title stayed the same.