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I am confused on how to compute the closure under a set of FDs. The actual question that I have is

Relation R{A, B, C, D, E} satisfies the following FDs: A→D AB → C E→B

Compute the closure of {A,E}+ under this set of FD. Also what is the candidate key?

Here is what I thought the answer would be but I have no idea if I am correct. I tried looking it up online, but nothing really helped me out. So hopefully someone here can help me.

A→A
A→AB
A→ABCD
A→ABCDE

A candidate key would be A.

Is this correct? Also I don't know why the formatting looks weird.... I indented 4 spaces for code....

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  • What are the instructions for computing the closure of a set of FDs? How did you come up with what you thought was the answer? What are the instructions for determining a CK? How did you come up with A as a CK? Show "effort". – philipxy Oct 15 '14 at 00:54
  • @philipxy I honestly don't know, thats why I asked on here for help. I couldn't find a good answer online when I googled it. Can you point me towards a good site for help? – ryan Oct 15 '14 at 03:17
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    But you were given an assignment, what resources were you told to use? I just googled "stackoverflow compute closure of a set of functional dependencies" and the second hit had an algorithm & references. Also: you "honestly don't know" how the possible answer got into your question?? – philipxy Oct 15 '14 at 05:27
  • You were asked to compute the closure of AE. You computed the closure of A, and you did *that* incorrectly. A->B is not true, for example. Neither is A->E. Which textbook did your teacher assign? Look in it for an algorithm to compute the closure of a set of attributes. – Mike Sherrill 'Cat Recall' Oct 27 '14 at 03:35

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