GATE | GATE-CS-2002 | Question 50
From the following instance of a relation scheme R (A, B, C), we can conclude that :
(A) A functionally determines B and B functionally determines C
(B) A functionally determines B and B does not functionally determine C
(C) B does not functionally determine C
(D) A does not functionally determine B and B does not functionally determine C
Explanation: Generally Normalization is done on the schema itself.
From the relational instance given,we may strike out FD s that do not hold.
e.g.B does not functionally determine C(This is true).
But we cannot say that A functionally determines B for the entire relation itself. This is because that, A->B holds for this instance, but in future there might be some tuples added to the instance that may violate A->B.
So overall on the relation we cannot conclude that A->B, from the relational instance which is just a subset of an entire relation.
Refer https://www.geeksforgeeks.org/introduction-of-database-normalization/ for more details.
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