Answered: in a database system the functional…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Question

If in a database system the functional dependency preservation within relations is critically important, then in relational database design:

(a) we can guarantee to achieve 3NF, but may have to sacrifice the lossless-join property.
(b) we can guarantee to achieve 3NF and the lossless-join property.
(c) we can guarantee to achieve BCNF and the lossless-join property.
(d) none of the above

Expert Solution

Step 1

If in a database system the functional dependency preservation within relations is critically important, then we cannot guarantee to achieve the given conditions in relational database design.

Hence the correct answer of the given problem is option “(d)”.

Step 2

Explanation of solution:

None of the above:

Dependency preservation :If we have a relation R with functional dependency F, then we can decompose the relation R into R1, R2....Rn.
Let’s assume that the functional dependency F’=F1 U F2 U....Fn. where F1 refers to the functional dependency of relation R1 and U refer to the Union operation.
This decomposition is dependency preserving if F’=F or (F’)⁺=F⁺.
And dependency preserving cannot guarantee to achieve the lossless join property.

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