Sunday, 10 May 2020

Distributed Database Question Bank with Answers 14

Distributed  and parallel database questions and answers for University exams


Question:

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


Answer:
Completeness
All tuples from the original relation are accounted for; as long as the selection predicates are complete, the resulting fragmentation will be complete.
Reconstruction
Reconstruction is performed by the union operator. By applying union to all horizontal fragments resulting from fragmentation of the original relation R, we MUST be able to get the original relation as the result.
Disjointness
A tuple t from one fragment of relation R may NOT appear in any other fragment of relation R; disjointness is guaranteed as long as the min-term predicates are disjoint.

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