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selft doubt

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Consider the relation scheme R(A, B, C, D, E, H) and the set of functional dependencies-

A → B

BC → D

E → C

D → A

  • Determine all essential attributes of the given relation.
  • Essential attributes of the relation are- E and H.
  • So, attributes E and H will definitely be a part of every candidate key.

So candidate keys are AEH, BEH, and DEH. 
 

Now, we can see A is proper subset of AEH. 

And B is proper subset of BEH (another candidate key). 
 

A union B is AB, which is not a proper subset of any candidate key. So, we can’t consider the given statement to be true. 

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