It is stated that every time an attribute X is appeared, the same value of Y…
2021
It is stated that every time an attribute X is appeared, the same value of Y is matched and a different value of Z is matched. Thus, it is clear that
- A.
X→Y
- B.
X→Z
- C.
X→(Y,Z)
- D.
(Y,Z)→X
- E.
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Correct answer: A
Given that every time attribute X appears, the same value of Y is matched, this indicates that X functionally determines Y, i.e., X→Y. However, a different value of Z is matched each time X appears, meaning Z is not uniquely determined by X. Therefore, X does not determine Z, and X→Z is invalid. Since X determines Y but not Z, the dependency X→(Y,Z) is also invalid. The reverse dependency (Y,Z)→X is not supported because the statement does not indicate that Y and Z together determine X. Based on this, the only valid functional dependency is X→Y.