Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
| Question 497 |
Suppose R is a relation schema and F is a set of functional dependencies on R. Further, suppose R1 and R2 form a decomposition of R. Then the decomposition is a lossless join decomposition of R provided that :
| R1 ∩ R2 → R1 is in F+ | |
| R1 ∩ R2 → R2 is in F+ | |
| both R1 ∩ R2 → R1 and R1 ∩ R2 → R2 functional dependencies are in F+ | |
| at least one from R1 ∩ R2 → R1 and R1 ∩ R2 → R2 is in F+ |
Question 497 Explanation:
Suppose R is a relation schema and F is a set of functional dependencies on R. Further, suppose R1 and R2 form a decomposition of R. Then the decomposition is a lossless join decomposition of R provided that at least one from
R1 ∩ R2 → R1 and R1 ∩ R2 → R2 is in F+
Lossless join:
The decomposition is a lossless-join decomposition of R if at least one of the following functional dependencies are in F+ (where F+ stands for the closure for every attribute or attribute sets in F):
R1 ∩ R2 → R1
R1 ∩ R2 → R2
R1 ∩ R2 → R1 and R1 ∩ R2 → R2 is in F+
Lossless join:
The decomposition is a lossless-join decomposition of R if at least one of the following functional dependencies are in F+ (where F+ stands for the closure for every attribute or attribute sets in F):
R1 ∩ R2 → R1
R1 ∩ R2 → R2
Correct Answer: D
Question 497 Explanation:
Suppose R is a relation schema and F is a set of functional dependencies on R. Further, suppose R1 and R2 form a decomposition of R. Then the decomposition is a lossless join decomposition of R provided that at least one from
R1 ∩ R2 → R1 and R1 ∩ R2 → R2 is in F+
Lossless join:
The decomposition is a lossless-join decomposition of R if at least one of the following functional dependencies are in F+ (where F+ stands for the closure for every attribute or attribute sets in F):
R1 ∩ R2 → R1
R1 ∩ R2 → R2
R1 ∩ R2 → R1 and R1 ∩ R2 → R2 is in F+
Lossless join:
The decomposition is a lossless-join decomposition of R if at least one of the following functional dependencies are in F+ (where F+ stands for the closure for every attribute or attribute sets in F):
R1 ∩ R2 → R1
R1 ∩ R2 → R2
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