Database Questions and Answers – Entity-Relationship Diagrams

This set of Database Multiple Choice Questions & Answers (MCQs) focuses on “Entity-Relationship Diagrams”.

1. Which of the following gives a logical structure of the database graphically?
a) Entity-relationship diagram
b) Entity diagram
c) Database diagram
d) Architectural representation
View Answer

Answer: a
Explanation: E-R diagrams are simple and clear—qualities that may well account in large part for the widespread use of the E-R model.

2. The entity relationship set is represented in E-R diagram as
a) Double diamonds
b) Undivided rectangles
c) Dashed lines
d) Diamond
View Answer

Answer: d
Explanation: Dashed lines link attributes of a relationship set to the relationship set.

3. The Rectangles divided into two parts represents
a) Entity set
b) Relationship set
c) Attributes of a relationship set
d) Primary key
View Answer

Answer: a
Explanation: The first part of the rectangle, contains the name of the entity set. The second part contains the names of all the attributes of the entity set.

4. Consider a directed line(->) from the relationship set advisor to both entity sets instructor and student. This indicates _________ cardinality
a) One to many
b) One to one
c) Many to many
d) Many to one
View Answer

Answer: b
Explanation: This indicates that an instructor may advise at most one student, and a student may have at most one advisor.

5. We indicate roles in E-R diagrams by labeling the lines that connect ___________ to __________
a) Diamond , diamond
b) Rectangle, diamond
c) Rectangle, rectangle
d) Diamond, rectangle
View Answer

Answer: d
Explanation: Diamond represents a relationship set and rectangle represents a entity set.
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6. An entity set that does not have sufficient attributes to form a primary key is termed a __________
a) Strong entity set
b) Variant set
c) Weak entity set
d) Variable set
View Answer

Answer: c
Explanation: An entity set that has a primary key is termed a strong entity set.

7. For a weak entity set to be meaningful, it must be associated with another entity set, called the
a) Identifying set
b) Owner set
c) Neighbour set
d) Strong entity set
View Answer

Answer: a
Explanation: Every weak entity must be associated with an identifying entity; that is, the weak entity set is said to be existence dependent on the identifying entity set. The identifying entity set is said to own the weak entity set that it identifies. It is also called as owner entity set.

8. Weak entity set is represented as
a) Underline
b) Double line
c) Double diamond
d) Double rectangle
View Answer

Answer: d
Explanation: Weak entity set is represented as a double rectangle in entity relationship diagram.

9. If you were collecting and storing information about your music collection, an album would be considered a(n) _____
a) Relation
b) Entity
c) Instance
d) Attribute
View Answer

Answer: b
Explanation: An entity set is a logical container for instances of an entity type and instances of any type derived from that entity type.

10. What term is used to refer to a specific record in your music database; for instance; information stored about a specific album?
a) Relation
b) Instance
c) Table
d) Column
View Answer

Answer: b
Explanation: The environment of database is said to be an instance. A database instance or an ‘instance’ is made up of the background processes needed by the database.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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