Sunday, 10 May 2020

Distributed Database Question Bank with Answers 15

Distributed  and parallel database questions and answers for University exams


Question:

List all correctness criteria for vertical data fragmentation in distributed database. Explain the role of each of the listed conditions. 


Answer:
Completeness
Each attribute of the original relation MUST be assigned to one of the fragments; this is guaranteed by the PARTITION algorithm.
Reconstruction
Reconstruction is performed by the join operator. By joining all vertical fragments resulting from fragmentation of the original relation R, we MUST be able to get the original relation as the result.
Disjointness
The key attributes are replicated in each fragment in the case of vertical fragmentation, so the fragments are never ‘completely’ disjoint. However, they are considered to be disjoint if non-key attributes from the original relation R appear in only one fragment.

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