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4. Database Design Principles > 4.4. Functional Dependencies

Functional Dependencies

Before we can discuss the other normal forms, we need to discuss the concept of functional dependency , which is used to define these normal forms. This concept is quite simple, and we have actually been using it for some time now. As an example, we have remarked that, for the Publishers table scheme, the PubName attribute depends completely on the PubID attribute. (More properly, we should say that the value of the PubName attribute depends completely on the value of the PubID attribute, but the earlier shorthand is convenient.) Thus, we can say that the functional dependency from PubID to PubName, written:

PubID PubName

holds for the Publishers table scheme. This can be read “PubID determines PubName” or “PubName depends on PubID.”


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