Decomposition of a relation R into R1 and R2 is a lossless-join decomposition if at least one of the following functional dependencies are in F+ (Closure of functional dependencies)
R1 ∩ R2 → R1 OR R1 ∩ R2 → R2
Question 1:
Let R (A, B, C, D) be a relational schema with the following functional dependencies:
A → B, B → C, C → D and D → B. The decomposition of R into (A, B), (B, C), (B, D)
(A) gives a lossless join, and is dependency preserving
(B) gives a lossless join, but is not dependency preserving
(C) does not give a lossless join, but is dependency preserving
(D) does not give a lossless join and is not dependency preserving
Refer this for solution.
Question 2
R(A,B,C,D) is a relation. Which of the following does not have a lossless join, dependency preserving BCNF decomposition?
(A) A->B, B->CD
(B) A->B, B->C, C->D
(C) AB->C, C->AD
(D) A ->BCD
Refer this for solution.
Below is the Quiz of previous year GATE Questions
http://quiz.geeksforgeeks.org/dbms/database-design-normal-forms/
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above
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