Consider the following relations and FDs and answer questions: 1) What are all t

Question

Consider the following relations and FDs and answer questions:

1) What are all the nontrivial FD’s that following from the given FDs? You should restrict yourself to FDs with single attributes on the right side.

2) What are all the keys of R?

3) What are all the superkeys for R that are not keys?

a. R(A, B, C, D) and FDs: AB->C, C->D, and D->A

b. R(A, B, C, D) and FDs: A->B, B->C, and B->D

c. R(A, B, C, D) and FDs: AB->C, BC->D, CD->A, and AD->B

d. R(A, B, C, D) and FDs: A->B, B->C, C->D, and D->A

Explanation / Answer

1) Non-trivial FD's =

a. AB->C, C->D

b.A->B, B->C, B->D

c.AB->C, BC->D

d. A->B,B->C,C->D

2)KEYS=

a. AB

b. A

c.AB, BC, CD

d.A, B, C, D

3)SUPERKEYS for R that are not keys=

a.CB,CDB

b.AB

c.ABD

d.All are keys hence,there can be no more superkeys for R that are not keys.

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