RDBMS Multiple Choice Questions on “Features of Good Relational Designs”.
1. Which of the following is not a feature of a good relational design?
a) Specifying primary keys
b) Specifying foreign keys
c) Preserving integrity constraints
d) Allowing redundancy of attributes
Answer: d
Clarification: Allowing redundancy of attributes makes it very difficult for data extraction. So, It is not a good relational design feature.
2. The dependency rules specified by the database designer are known as _______
a) Designer dependencies
b) Database rules
c) Functional dependencies
d) None of the mentioned
Answer: c
Clarification: The dependency rules specified by the database designer are known as functional dependencies. The normal forms are based on functional dependencies.
3. If the decomposition is unable to represent certain important facts about the relation, then such a decomposition is called as?
a) Lossless decomposition
b) Lossy decomposition
c) Insecure decomposition
d) Secure decomposition
Answer: b
Clarification: If the decomposition is unable to represent certain important facts about the relation, then such a decomposition is called as lossy decomposition. Lossy decompositions should be avoided as they result in the loss of data.
4. If the decomposition is able to represent all the facts about the relation then such a decomposition is called as?
a) Lossless decomposition
b) Lossy decomposition
c) Insecure decomposition
d) Secure decomposition
Answer: a
Clarification: If the decomposition is able to represent all the facts about the relation then such a decomposition is called as a lossless decomposition. Lossless decompositions are generally preferred.
5. A domain whose elements are indivisible is called as ______
a) Unique domain
b) Proxy domain
c) Atomic domain
d) Multiple domain
Answer: c
Clarification: A domain is said to be atomic if all of its elements are considered to be indivisible. If the domains are atomic, then the relational schema is in the first normal form.
6. If all the domains are atomic then the relational schema is in ________ normal form
a) 1
b) 2
c) 3
d) 4
Answer: a
Clarification: If all the domains are atomic then the relational schema is in first (1) normal form. That is, the domains must be indivisible.
7. State true or false: Composite attributes have non-atomic domains.
a) True
b) False
Answer: b
Clarification: Composite attributes have non atomic domains i.e. domains of the composite attributes are generally divisible.
8. State true or false: Redundancy is desired in a relational schema
a) True
b) False
Answer: b
Clarification: Redundancy is never desired in a relational schema, it makes data retrieval very difficult.