Chapter 4

Question 1

Identify the main characteristics of entity relationship components

Answer 1

The ER model’s main components are entities, attributes, relationships, and constraints. Entities are unique persons, places, things, or concepts represented as rectangles in ER diagrams. Attributes describe entity characteristics and can be simple, composite, or derived. Relationships describe associations between entities and are represented by connecting lines.

Question 2

Describe how relationships between entities are defined, refined, and incorporated into the database design process

Answer 2

Relationships are defined using business rules, which are precise descriptions of organizational policies. Nouns translate into entities, verbs into relationships. Relationships are classified as one-to-many (1:M), many-to-many (M:N), or one-to-one (1:1). Relationships have cardinality (min/max) and participation (mandatory/optional). In relational databases, relationships use foreign keys; many-to-many requires a composite entity.

Question 3

Explain how ERD components affect database design and implementation

Answer 3

The ERD is the conceptual blueprint for the database. Entities map to tables, attributes to columns, and primary keys to table keys. Relationships are implemented via foreign keys. The relational model provides structural independence and logical data representation. ERDs help visualize data, define relationships and constraints, and guide normalization to reduce redundancy and anomalies.

Question 4

Describe how real-world database design often requires the reconciliation of conflicting goals

Answer 4

Database design balances design standards (minimizing redundancy and anomalies), processing speed (query and transaction efficiency), and information requirements (accurate, complex reporting). Normalization ensures design elegance but can reduce speed due to joins. Sometimes denormalization is used to improve performance at the risk of anomalies. Documentation is critical throughout design.