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Statement for Linked Answer Questions 52 and 53:
Relation R has eight attributes A B C D E F G H. Fields of R contain only atomic values. F = {C H → G, A → BC, B → C F H, E → A, F → E G} is a set of functional dependencies (FDs) so that F+ is exactly the set of FDs that hold for R.
Q.52 How many candidate keys does the relation R have?
- 3
- 4
- 5
- 6
Correct answer: 4
Solution
Attribute D never appears on any FD right-hand side, so it must belong to every candidate key. Testing minimal supersets, the closures of AD, BD, DE, and DF each yield all eight attributes, and these are the only minimal keys. There are 4 candidate keys (option index 1), not the stored 6.
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