Dependency preservation, Database Management System

Assignment Help:

Dependency Preservation

It is obvious that the decomposition must be lossless so that we do not lose any information from the relation that is decomposed. Dependency preservation is another main requirement since a dependency is a constraint on the database. If each attributes appearing on the left and the right side of a dependency appear in the similar relation, then a dependency is considered to be preserved. Therefore, dependency preservation can be checked simply. Dependency preservation is important, because as stated previously, dependency is a constraint on a relation. Therefore, if a constraint is split over more than one relation (dependency is not preserved), the constraint would be complex to meet. We will not talk about this in more detail in this unit.  You may refer to the more readings for more details. Though, let us state one basic point:

"A decomposition into 3NF is lossless and dependency preserving whereas a decomposition into BCNF is lossless but may or may not be dependency preserving."

 


Related Discussions:- Dependency preservation

ER diegrams, How to draw an ER diagram to a finance companz

How to draw an ER diagram to a finance companz

Linked list, what is difference between circular inked lust and grunded lin...

what is difference between circular inked lust and grunded linked list

RDM & ER Modelling, #questiRegional Gardens has many nurseries, including W...

#questiRegional Gardens has many nurseries, including Wagga Wagga, Bathurst, Albury, Orange, and Dubbo. Each nursery is known by its campus code, eg WW, B, A, O and D respectively.

DSS, WHAT IS DSS? WRITE ITS REQUIREMENTS.

WHAT IS DSS? WRITE ITS REQUIREMENTS.

Discuss the concept of data independence, Question: a) Discuss the conc...

Question: a) Discuss the concept of data independence, explaining its importance in a database environment. b) To address the issue of data independence, the ANSI-SPARC t

Develop a fragment of a hypothetical system, The objectives of this assignm...

The objectives of this assignment are:  - to develop skills in the design of database driven applications  - to develop skills in applying SQL to implement the relational and

Define what Immediate database modification technique uses, Define what Imm...

Define what Immediate database modification technique uses?  Ans: Both undo and redo.

Log, what is the need of a log in dbms

what is the need of a log in dbms

Data control, Identify the need and use of data control through problem sol...

Identify the need and use of data control through problem solving, illustration

Illustrate system design of an object oriented approach, System Design: An ...

System Design: An Object Oriented Approach Any software systems always try to change and evolve as technology and business rules evolve. The development of information systems

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd