Answer to Question #55804 in Programming & Computer Science for Jiahao Qi

Question

Given the following table, which of the following a
re NOT functional dependencies:
a) A ->B
b) B -> A
c) (B, C) -> D
d) B -> D
e) (B, C) -> E

A B C D E (The letters A, B, C, D, and E) are columns.
X Y U L G
X Y M K H
X T U J H
W Z M J I
W Z N J I

Answer 1

Solution
We can assume, that some expression is functional dependencies if for same value of left side we have same value at the right.
So, a) not functional dependencies since for A=X corresponding 2 rather value for B (Y and T).
d) not functional dependencies since for B=Y corresponding 2 rather value for D (L and K).
for all other dependencies for same value of left side corresponding same value in right side

Answer: A, D