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Given R(A,B,C,D,E) which of the following two sets of functional dependencies make R a relation in 2NF?

F1={DE→ABC,E→C}

Vs.

F2={DE→ABC,C→E}

I almost sure that the F1 is not in 2NF and the F2 is in 2NF (as C does not depend on E — it's backward). But why doesn't the second one a 3NF?

I am basing my assumption on What are 1NF, 2NF and 3NF in database design?

Also I would be glad to get an example where F is modified so it would match 3NF — I want to know if there is another option/possibility than just {DE→ABC}.

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  • "Almost sure"? Please show your reasoning. – philipxy Feb 05 '15 at 13:27
  • @philipxy Already said - based on the link I gave. Since C depends on E and E is only part of the PKEY, it is 2NF. – Guy Feb 05 '15 at 19:22
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    *"Since C depends on E and E is only part of the PKEY, it is 2NF."* Should read "Since C is a non-prime attribute, C depends on E, and E is only part of a candidate key, R is *not* in 2NF." You have to consider all the candidate keys, not just a primary key. – Mike Sherrill 'Cat Recall' Feb 05 '15 at 22:05
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    1. Giving a link is not showing your reasoning. Thanks for the comment. Please edit it into your question. Also for C->E. 2. Your writing is unclear. If you are trying to say that you believe the first is not in 2NF and the second is in 2NF unless you have made an error then please say so. Also your parenthetical text is unintelligble. 3. You need to learn definitions and use them exactly. See [this](http://stackoverflow.com/a/27504915/3404097). – philipxy Feb 05 '15 at 22:21
  • @philipxy "If you are trying to say that you believe the first is not in 2NF and the second is in 2NF" - This. I edited my post – Guy Feb 07 '15 at 20:04
  • Thank for the edit but most problems remain. You don't use relevant terms or parts of definitions of NFs in your (unclear) reasoning. Unlike MikeSherrill'CatRecall' 's comment. There are a bunch of terms to know and steps to follow to determine a relation's highest normal form. My link gives definitions. Use NF definitions to show whether R & F1/F2 satisfy them. Like I said there, "an answer to your question is effectively a textbook's chapter on normalization". I have no time to write that as a question now. What textbook(s)/reference(s) were you given? Your SO link is unclear & useless. – philipxy Feb 08 '15 at 03:02

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