Functional Dependencies and Normal Forms

normalization

I'm trying to grasp the concepts of functional dependencies and normal forms, specifically first (1NF), second (2NF), and third (3NF) normal forms. The link here was extremely helpful in deciding the distinction between the three forms, but I have a much more abstract problem.

The accepted answer to this post gives wonderful examples of tables and which normal form they are in. However, my question poses the following:

For (W X Y Z), determine the form of: WX->Y, WX->Z, Y->Z. (Note: 'WX' should be underlined as the combined primary key, but I couldn't find that in the formatting, so it's bold)

I don't get it; how can I even begin to do this? The textbook I'm referencing only gives concrete examples, and I don't understand the theory well enough to apply it to the abstract. Any insight?

Best Answer

  1. 1NF satisfied, as Y and Z depend on the key WX;
  2. 2NF satisfied as Y and Z depend on the whole key WX, and not on any subset of the key;
  3. 3NF not satisfied as Z depends on Y, which is not part of the key.

To put this into 3NF one would restructure as (W X Y) and (Y Z).

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