RDBMS Multiple Choice Questions on “Extended ER Features”.
1. The process of designating sub groupings within the entity set is called as _______
a) Specialization
b) Division
c) Aggregation
d) Finalization
Answer: a
Clarification: The process of designating sub-groupings within the entity set is called as specialization. Specialization allows us to distinguish among entities.
2. State true or false: Specialization can be applied only once
a) True
b) False
Answer: a
Clarification: We can apply specialization multiple times to refine a design. An entity set may also be specialized by more than one distinguishing feature.
3. Which of the following is the specialization that permits multiple sets
a) Superclass specialization
b) Disjoint specialization
c) Overlapping specialization
d) None of the mentioned
Answer: c
Clarification: Overlapping specialization is the type of specialization that permits multiple sets. But disjoint specialization does not permit multiple sets. Disjoint specialization permits at most one set.
4. The similarities between the entity set can be expressed by which of the following features?
a) Specialization
b) Generalization
c) Uniquation
d) Inheritance
Answer: b
Clarification: The similarities between the entity set can be expressed by the generalization feature. It is a containment o the relationship that exists between a higher level entity set and one or more lower level entity sets.
5. Higher level entity sets are designated by the term _________
a) Sub class
b) Super class
c) Parent class
d) Root class
Answer: b
Clarification: Higher level entity sets can also be designated by the term super class. In the similar manner lower level entity sets can also be designated by the term sub class.
6. State true or false: The attributes of the higher level entity sets are inherited by the attributes of the lower level entity sets
a) True
b) False
Answer: a
Clarification: The attributes of the higher level entity sets are inherited by the attributes of the lower level entity sets. But the inverse is not true in this case.
7. Which of the following is not a generalization constraint?
a) Condition-defined
b) User defined
c) Disjoint
d) Machine defined
Answer: d
Clarification: Machine definition is not a generalization constraint. Condition defined, user defined, disjoint and overlapping are 4 generalization constraints.
8. Condition defined generalization constraint is also said to be ________
a) Attribute defined
b) Constraint defined
c) Value defined
d) Undefined
Answer: a
Clarification: Condition defined generalization constraint is also said to be attribute defined.
9. If each higher level entity belongs to the lower level entity, then what kind of generalization is it?
a) Modal generalization
b) Partial generalization
c) Total generalization
d) None of the mentioned
Answer: c
Clarification: If each higher level entity belongs to the lower level entity then it is called as total generalization. It is also called as total specialization. If some higher level entities do not belong, it is called as partial generalization.
10. ________ is an abstraction through which relationships are treated as higher level entities
a) Creation
b) Superseding
c) Attribute separation
d) Aggregation
Answer: d
Clarification: One limitation of E-R model is that it cannot express relationships among relationships. Thus for this purpose, aggregation is used. Aggregation is an abstraction through which relationships are treated as higher level entities.