RDBMS Questions and Answers for Experienced people on “Entity Relationship Model”.
1. The _________ of the entity set is an actual collection of entities belonging to that entity set.
a) Extension
b) Intention
c) Description
d) Availability
Answer: a
Clarification: The extension of the entity set is an actual collection of entities belonging to that entity set.
2. A ___________ is an association among several entities.
a) Relationship
b) Association
c) Set
d) Combination
Answer: a
Clarification: A relationship is an association among several entities. A relationship specifies how two entities are related.
3. The attributes of a relationship are called as _________ attributes
a) Relational
b) Conjunctive
c) Descriptive
d) None of the mentioned
Answer: c
Clarification: A relationship may also have attributes. These attributes are called as descriptive attributes.
4. What are composite attributes?
a) They are those attributes which cannot be further divided into other attributes
b) They are those attributes which can further be divided into other attributes
c) They are those attributes which are essentially the primary keys of the relation
d) None of the mentioned
Answer: b
Clarification: Composite attributes are the ones which can be further divided into other attributes whereas simple attributes cannot be divided into other attributes.
5. Let E be an entity set in a relationship set R. If every entity in E participates in at least one relationships in R, Then the participation of E in R is __________
a) Partial
b) Total
c) Complete
d) Incomplete
Answer: Total
Clarification: Let E be an entity set in a relationship set R. If every entity in E participates in at least one relation in R, Then the participation of E in R is total.
6. Let E be an entity set in a relationship set R. If only some entities in E participate in relationships in R, Then the participation of E in R is __________
a) Partial
b) Total
c) Complete
d) Incomplete
Answer: Total
Clarification: Let E be an entity set in a relationship set R. If only some entities in E participate in relationships in R, Then the participation of E in R is partial.
7. State true or false: We cannot specify keys in the Entity-Relationship model
a) True
b) False
Answer: b
Clarification: Keys can be specified in the entity-relationship model to uniquely identify the entity in the entity set.
8. State true or false: Multiple attributes combined together can be primary keys
a) True
b) False
Answer: a
Clarification: A primary key is an attribute or a set of attributes that can uniquely identify a tuple in a relation. So, this means that multiple attributes can be combined to uniquely identify a tuple in a relation.
9. Which of the following is a good database management practice?
a) Adding redundant attributes
b) Removing redundant attributes
c) Not specifying primary keys
d) None of the mentioned
Answer: b
Clarification: Removing redundant attributes from a relation makes data extraction more efficient and faster. Thus, it is a good database management technique.