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