Question

Suppose that we pick the following three tuples from a legal instance of a relation S (S has 100 tuples in total). Relation S has the following schema: (A : integer, B : integer, C : integer). The three tuples are: (1,2,3), (4,2,3), and (5,3,3). Which of the following dependencies can you infer does not hold over S?
A. A → B,
B. BC → A,
C. C → B

Answer 1

Answer:

The correct answer is BC → A, A does not hold over S. we noticed the tuples (1 ,2 ,3 ) and (4 ,2 ,3) which can hold over S)

Explanation:

Solution

No, since in this case the instance of S is provided. so such particular dependencies are unable to breach through such instance, but unable to tell which the dependencies hold towards S.

A functional dependency holds towards only when a relation forms a statement regarding the complete allowed instances of relation.