Question

 3NF is inadequate in situations where the relation:
A. has multiple candidates key
B. has candidate key that are composite
C. has overlapped candidate keys
D. all the above

Comments

what is the source of the question,bcoz it doesn't seem valid question to me

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The question is mentioned in the Made Easy Workbook

Answer 1

The original definition of 3NF was inadequate in some situations. It was not satisfactory for the tables:
- that had multiple candidate keys
- where multiple candidate keys were composite
- where the multiple candidate keys overlapped.

Therefore, a new normal form, the BCNF was introduced.

ref: https://books.google.co.in/books?id=pHVCBANDsRgC&pg=PA82&lpg=PA82&dq=3NF+is+inadequate+in+situations+where+the+relation:&source=bl&ots=qlrTtU1T51&sig=LDpDrZ8NFn1d1UQ0_6vxsh5sWDQ&hl=en&sa=X&ved=0ahUKEwjPzu-GvbXWAhXMLo8KHRDOCY0Q6AEIUDAH#v=onepage&q=3NF%20is%20inadequate%20in%20situations%20where%20the%20relation%3A&f=false

Answer 2

Option A,B,C are motivation for BCNF.

Comments

But doesn't C imply both A and B? Am I missing something?

Answer 3

If candidate key is composite and there is a chance of partial dependency then only 3NF is inadequate . But otherwise all three situation is cause no problem with 3NF

Comments

C can determine A or vice verse and thus cause anomalies but 3NF conditions are satisfied.

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ok ,so in overlapping keys there must be some dependency. And that dependency causes anomalies.but here all r prime attribute .So it not causing any problem

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Yes. Actually it is causing problem- but not violating "3NF" and so BCNF came.

Answer 4

Its D -all the above, all three conditions can favour BCNF

Comments

Can you please explain, Sir?

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answer should be (c)

3NF is adequate for composite candidate key and for multiple candidate key..

3NF allows FDs where 1) the FD is trivial 2) the left side of the FD is a candidate key or 3) the right side of the FD is a key attribute (an attribute used to make any key). 

Due to overlapping of the candidate keys, BCNF came which allows 1 and 2 but not 3

u can see : http://dba.stackexchange.com/questions/81310/what-exactly-is-overlapping-candidate-key

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All the three conditions above have a chance of having partial dependencies. So it's not in 2NF thus inadequate for being 3NF.