normalization

Question

Can you explain me this :

A table is in second normal form if every attribute is determined by every candidate key , but is not determined by any pure subset of Candidate key ?

True or false

Comments

if in the relation if [prime attribute--------> non prime attribute] then the relation not in 2nd normal form

if in the relation if[prime attribute------>prime attribute] then the relation in 2nd and 3rd normal form

Answer 1

A relation is not in 2NF if it is suffering from partial dependency..
Partial dependency means proper or pure  subset of candidate key produces non prime attribute...
non key ---> non key  allowed in 2NF.
Proper Subset of candidate key -----> non prime : Partial Dependency.
A candidate key always determines each and every attribute of relation...

Comments

Yeah i got you . so answer is false right ?

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true..
why false ??

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SORRY BUT I AM GETTING CONFUSED JUST HOLD ON !

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if partial dependency is there.... than the relation is not in 2NF!!

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Precisely from the statements.

pure subset of Ck ie,Prime attributes.

Now,CK would functionally determine every attribute.(every attribute is determined by every candidate key )

From the statement,pure subset of Candidate key do not determine every attribute(which can be Prime or non prime).

P->NP/P

So,there are no P->NP ie.no Partial dependency.

Hence relation is in 2NF.TRue