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Number of candidate keys

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Let R(ABCDE) be a relational schema and F={AB->CD, ABC->E,C->A}. The number of candidate keys are

a) 1

b) 2

c) 3

d) 4

Is there some standard way to solve such problem.. or we have to consider each Functional Dependency...?Please explain...
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2 Answers

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by lookin at the RHS side u willcome to know B is nowhere so B has to be a part of CK so u vil get two CK AB and BC
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Option B.

Super key is AB, BC and ABC
->A candidate key is minimal super key  
 Candidate key is AB and BC but not ABC
so,

2 is Right  Answer
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