Question

Suppose that we have the following three tuples in a legal instance of a relation

schema S with three attributes ABC (listed in order): (1,2,3), (4,2,3), and (5,3,3).
Which of the following dependencies can you infer does not hold over schema S?
(a) A -> B, (b) BC -> A, (c) B -> C

Answer 1

(b) BC → A

Step-by-step explanation:

For given instance of S, certain dependencies (that is to say, A → B and B → C) can be said that they are not violated by this instance of S.

It can be said that an FD holds with respect to a relationship is to make a claim about all appropriate instances of S.

BC → A does not hold over S. To confirm, let's look at the tuples (1, 2, 3) and (4, 2, 3).

Hence, the answer is (b) BC → A.