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R(A,B,C,D,E) Functional Dependencies = {AC->E,B->D,E->A}

I know ABC is a candidate key.Can BC be a candidate key too?

theavatar
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  • What happens when 1. you look at the definition of "CK" or 2. you use the method you used for finding the first CK to finding all the other CKs? – philipxy Mar 19 '17 at 16:10
  • The question in your title is not the question in your question. What is your question? – philipxy Mar 19 '17 at 22:57

2 Answers2

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The definition of "candidate key" is a superkey that does not contain another superkey. So a candidate key does not contain another candidate key.

philipxy
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I could tell that BC is not a candidate key. For (ABC)+, you could get the attribute D and E through the functional dependency and thus you get a key by involving all the attributes.

However, for (BC)+, you could only get D, you cannot get A or E. Thus, BC is not a candidate key.

messfish
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