RDBMS Multiple Choice Questions on “Decomposition Algorithms”.
1. What does the BCNF decomposition algorithm do?
a) States a method to decompose a relation satisfying BCNF
b) States a method for joining two relations satisfying BCNF
c) States a method to decompose a relational schema such that there are no multiple occurrences
d) None of the mentioned
Answer: a
Clarification: If a relation is not in BCNF, it can be decomposed into simpler relations that are in BCNF. The BCNF decomposition algorithm states a method to decompose a relation satisfying BCNF.
2. The 3NF decomposition algorithm is also called as _______
a) 3NF normal algorithm
b) 3NF synthesis algorithm
c) 3NF generator
d) Functional dependence algorithm
Answer: b
Clarification: The 3NF decomposition algorithm is also called as 3NF synthesis algorithm since it takes a set of dependencies and adds one schema at a time, instead of decomposing the initial schema repeatedly.
3. Which of the following is desirable in a database design with functional dependencies?
a) BCNF
b) Losslessness
c) Dependency preservation
d) All of the mentioned
Answer: a good database design must satisfy BCNF, must be lossless, must be dependency preserving. These are the goals of database design with functional dependency.
4. State true or false: SQL specifies a way of mentioning functional dependencies
a) True
b) False
Answer: b
Clarification: SQL does not specify a way to mention functional dependencies. Functional dependencies are just used for theoretical improvement of database while implementing them in SQL later.
5. State true or false: Most current database systems do not support constraints on materialized view
a) True
b) False
Answer: a
Clarification: Most current database systems do not support constraints on materialized view.
6. Multi valued dependencies are also called as __________
a) Equality generating dependencies
b) Tuple generating dependencies
c) Multi-purpose dependencies
d) None of the mentioned
Answer: b
Clarification: Multi valued dependencies are also called as tuple generating dependencies because they require other tuples of a certain form to be present in the relation.
7. Functional dependencies are sometimes referred to as ________
a) Equality generating dependencies
b) Tuple generating dependencies
c) Multi-purpose dependencies
d) None of the mentioned
Answer: a
Clarification: Functional dependencies are sometimes referred to as equality generating dependencies because they require other tuples of a certain form to be present in the relation.
8. The _______ is a set of all functional and multi values dependencies implied by a set of functional dependencies
a) Star
b) Closure
c) Derivation
d) Evolution
Answer: b
Clarification: The closure is a set of all functional and multi values dependencies implied by a set of functional dependencies on a given relation. It is denoted by giving a “+” superscript.
9. State true or false: If a relational schema is in _______ NF and A is a subset of R and B is also a subset of R then it is that A is a superkey is a trivial multi values dependency.
a) 1
b) 2
c) 3
d) 4
Answer: d
Clarification: If a relational schema is in 4NF and A is a subset of R and B is also a subset of R then it is that A is a superkey is a trivial multi values dependency.
10. Which of the following normal forms does not exist?
a) BCNF
b) PJNF
c) 5NF
d) None of the mentioned
Answer: d
Clarification: All of the mentioned normal forms i.e. BCNF, PJNF, 5NF exist. BCNF is Boyce Codd normal form, 5NF is the fifth normal form and PJNF is project join normal form.