Attributes and normalization. Database question. Can someone explain the answer,

Question

Attributes and normalization. Database question. Can someone explain the answer, I will give good ratings for a correct response.

Consider the relation R(A, B, C, D, E, F, G, H, I, J, K). Suppose that the following functional dependencies hold on R: F = {{A} rightarrow {C, D, E}, {A, B, G, H} rightarrow {I, J, K, F}, {J, I, G, H} rightarrow {F, A, B}} Determine which sets of attributes form keys of R. How would you normalize this relation? Consider the relation R(A, B, C, D, E). If {A} rightarrow {D}, {B} rightarrow {C}, and {A, B} rightarrow {E}, argue using the generalized definition of the 3NF that this relation is not in 3NF.

Explanation / Answer

4.

The functional dependencies are divided into left,right or middle based on their position in dependencies

Now use closures

GH+ / GH  

adding middle attributes A and B

ABGH+ / ABCDEFGHIJK

So the set of attributes which can form the Key of R is {A,B,G,H}

Normalize the relation R based on functional dependencies

R1(A,C,D,E)

R2(A,B,G,H,I,J,K,F)

R3(J,I,G,H,F,A,B)

5.

The relation is not in 3NF as all the non key attributes ( C,D) are not fully functionally dependent on composite key attributes(A,B).

L M R G,H A,B,I,J C,D,E,F

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