Fifth Normal form is concerned with
- (A)
Join dependency
- (B)
Domain-key
- (C)
Multivalued dependency
- (D)
Functional dependency
ISRO CS 2023 Q.34: solution and answer
Answer and solution
ANSWER
Fifth Normal Form is concerned with join dependency, option (a).
Official answer: ASource: ISRO's revised and final answer key of 16 February 2024
Fifth Normal Form (5NF), also called Project-Join Normal Form (PJNF), is the highest of the classical normal forms.
A relation is in 5NF when every nontrivial join dependency that holds in it is implied by its candidate keys. Equivalently, the relation cannot be split into smaller relations and rejoined without losing information, unless the split follows from the keys.
So 5NF is concerned with join dependencies, which is option (a).
Option (b): Domain-Key Normal Form (DKNF) is a separate normal form defined through domain and key constraints. It is not 5NF.
Option (c): multivalued dependencies are the concern of Fourth Normal Form (4NF).
Option (d): functional dependencies drive 2NF, 3NF and BCNF.
KEY IDEA
Each normal form is tied to a kind of dependency. Functional dependencies lead to 2NF, 3NF and BCNF. Multivalued dependencies lead to 4NF. Join dependencies lead to 5NF, also called Project-Join Normal Form.
WATCH OUT FOR
Choosing multivalued dependency because 5NF comes straight after 4NF. 4NF removes nontrivial multivalued dependencies that are not implied by keys. 5NF goes further and handles join dependencies that are not implied by keys. Domain-Key Normal Form is a different normal form, not another name for 5NF.
From the ISRO CS 2023 paper. Every question of this paper · The full paper (PDF, ISRO) · All 3 ISRO Normal forms questions, with notes