Normalization

Question

Which of the following normal forms has dependency-preserving property?

a) 1NF

b) 2NF

c) 3NF

d) BCNF

Comments

3NF  ??

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To get a Clear Answer of this question, I mailed Prof. Korth, Navathe, & Sudarshan. Got their Reply, discussed in the below lecture:

Watch this: https://youtu.be/Epy_Vw4gFpo?feature=shared 

Answer 1

3NF guarantees dependency preservation.

Read this paper: http://homepages.inf.ed.ac.uk/libkin/papers/pods06b.pdf

Comments

Thanks @Kantikumar I brushed up the concepts, looks like upto 3NF decomposition is guranteed to be lossless and dependency preserving. Edited my previous comment.

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Any supporting material for 2NF having dependency preserving?

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I think 1NF,2NF and 3NF all guarantees lossless and dependency preserving decomposition

but 3NF is dependency preserving with less no. of redundancy so its better to design schema with 3NF for dependency preserving requirement

Answer 2

1 NF , 2NF, 3NF always preserve dependency , but sometime BCNF not  preserve dependency.

Comments

IS it true, anyone please confirm this @arjun @bikram

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yes its true

Answer 3

Only 3NF has property of FDs preserving along with the losseless decomposition.BCNF do not have such property .This is very very important as well as very crucial property.

Comments

I also want to know about 1NF and 2NF, does they preserve dependencies ?

Answer 4

3NF decomposition is both lossless-join and dependency-preserving

A Dependency-Preserving Lossles-Join 3NF Decomposition Algorithm

a.) Find minimal cover

b.) Put FDs agreeing on the left-hand-side in the same schema

c.) Have extra schema for a key, if none of the above schemas contain a key

Example R = {A,B,C,D,E,G,I,J}

a. ) F- ={A→B, A→E, A→D, AC→G}

b.) R1(ABDE), R2(ACG)

c,) R3(ACIJ)