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Attribute Closures
Concept of Attribute Closures and GATE, NET question
Prerequisite: Before seeing this chapter please follows previous chapters:
Properties of Functional Dependency
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Definition: Set of attributes that are functionally determined by X.
Example:
Let a relation R (ABCD) and Functional Dependencies are {A → B, B → C, C → D}
Now,
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Q. Gate – 2006:
The following functional dependencies are given:
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Which one of the following options is false?
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Solution:
We are finding the following attribute closure:
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So, option (C) is correct.
Q. UGC – 2014:
Let R=ABCDE is a relational scheme with a functional dependency set
F = {A → B, B → C, AC → D}. The attribute closures of A and E are
A. ABCD, ϕ
B. ABCD, E
C. Φ, ϕ
D. ABC, E
Solution:
R (ABCDE)
F = {A → B, B →C, AC → D)
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Answer:
Option (B) is correct.
