Chapter 2

Question 1

What is the first step in designing a database application?

Answer 1

Requirements Analysis

This step focuses on understanding what the database needs to achieve.

Question 2

What model is used during the conceptual design phase of database design?

Answer 2

ER Model

The ER Model helps identify entities and relationships within the enterprise.

Question 3

What information is considered during the conceptual design phase?

Answer 3

Entities, relationships, integrity constraints

This includes understanding what data to store and the rules governing it.

Question 4

What is a database schema in the context of the ER Model?

Answer 4

A representation of entities and relationships pictorially

Often depicted using ER diagrams.

Question 5

What is the purpose of logical database design?

Answer 5

Choose a DBMS and map an ER diagram into a relational schema

This step translates the design into a format suitable for implementation.

Question 6

What does schema refinement involve?

Answer 6

Analyzing the current schema to identify problems and refine it

This includes normalizing relations for performance.

Question 7

What is physical database design focused on?

Answer 7

Building indices and clustering tables

This step optimizes the physical storage of data.

Question 8

What does application and security design consider?

Answer 8

Aspects of the application beyond the database itself

This includes user permissions and application logic.

Question 9

Define ‘Entity’ in the context of the ER Model.

Answer 9

A real-world object distinguishable from other objects

An entity is described using a set of attributes in the database.

Question 10

What is an Entity Set?

Answer 10

A collection of similar entities

For example, all employees are an entity set.

Question 11

What is a primary key in an entity set?

Answer 11

A key that uniquely identifies each entity in the set

For example, SSN is a primary key for employees.

Question 12

What is a Relationship in the ER Model?

Answer 12

An association among two or more entities

For example, an employee works in a department.

Question 13

What is a Relationship Set?

Answer 13

A collection of similar relationships

This can involve multiple entities participating together.

Question 14

What are Participation Constraints?

Answer 14

Rules that define whether all or some entities must participate in a relationship

For example, does every department have a manager?

Question 15

Define ‘Weak Entity’.

Answer 15

An entity that can only be identified by considering the primary key of another entity

Weak entities require a one-to-many relationship with an owner entity.

Question 16

What is the identifying owner in a weak entity?

Answer 16

The primary key of the owner entity combined with a partial key

For example, SSN + pname can identify a weak entity.

Question 17

What are ISA hierarchies?

Answer 17

Hierarchies that define a subclass relationship among entities

For example, Contract_Emps and Hourly_Emps are subclasses of Employees.

Question 18

What is an overlap constraint in ISA hierarchies?

Answer 18

A constraint that determines if an entity can belong to multiple subclasses

By default, this is disallowed.

Question 19

What is a covering constraint in ISA hierarchies?

Answer 19

A constraint that specifies whether every entity must belong to a subclass

By default, this is not required.