Identifying the keys of a relvar from a set of functional dependencies

Question

Currently enrolled in a database theory class, and was sick during the explanation on functional dependencies. There is no textbook for this course so I've had to make do with Google so far. I've an assignment which asks, given a relvar and a list of function dependencies, to:

• Identify the keys of a relvar
• decompose the revlar into relvars that are in 3NF

Here are a couple of the problems on the assignment

a. R = ABCD, F = {AB>C, C>D, D>A}

b. R = ABCDE, F = {AB>C, C>D, D>B, D>E}

At least the keys seems like a simple process, but I've no algorithm for it! Any help is appreciated.

Answer 1

Well, make everything into 2 attribute tables and you have 5NF. Huuuzah!!

Answer 2

We might be in the same class, as I have the same assignment...

I did find this answer on a related question, which helped me understand the process for finding keys. Hope it helps.

https://stackoverflow.com/a/10164535

Answer 3

After some very frustrating searching, finally found a straight forward method! This professor At UHCL has produced a great series of videos addressing this very topic:

http://www.youtube.com/watch?v=s1DNVWKeQ_w

He also covers 2NF, 3NF, BCNF:

http://www.youtube.com/watch?v=nUbp9MRN0To