Process-Synchronization
October 11, 2023Software-Engineering
October 12, 2023Database-Management-System
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Question 102
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Let r be a relation instance with schema R = (A, B, C, D). We define r1 = ΠA,B,C(R) and r2 = ΠA,D(R). Let s = r1*r2 where * denotes natural join. Given that the decomposition of r into r1 and r2 is lossy, which one of the following is TRUE?
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s ⊂ r
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r ∪ s = r
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r ⊂ s
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r * s = s
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Question 102 Explanation:
Let us consider an example:
Table r: R(A, B, C, D)
Table r1: ΠA,B,C(R)
Table r2: ΠA,D(R)
S = r1 * r2 (* denotes natural join)
Table S:
Table r ⊂ Table S
⇒ r ⊂ S
Table r: R(A, B, C, D)
Table r1: ΠA,B,C(R)
Table r2: ΠA,D(R)
S = r1 * r2 (* denotes natural join)
Table S:
Table r ⊂ Table S
⇒ r ⊂ S
Correct Answer: C
Question 102 Explanation:
Let us consider an example:
Table r: R(A, B, C, D)
Table r1: ΠA,B,C(R)
Table r2: ΠA,D(R)
S = r1 * r2 (* denotes natural join)
Table S:
Table r ⊂ Table S
⇒ r ⊂ S
Table r: R(A, B, C, D)
Table r1: ΠA,B,C(R)
Table r2: ΠA,D(R)
S = r1 * r2 (* denotes natural join)
Table S:
Table r ⊂ Table S
⇒ r ⊂ S
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