Data Modeling Using the Entity-Relationship (ER) Model

Dr. Buleje

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Outline

? Overview of Database Design Process

? Example Database Application (COMPANY)

? ER Model Concepts

? Entities and Attributes

? Entity Types, Value Sets, and Key Attributes

? Relationships and Relationship Types

? ER Diagrams – Notation

? ER Diagram for COMPANY Schema

? Alternative Notations – UML class diagrams, others

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Overview of Database Design Process

? Two main activities:

? Database design

? Applications design

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Overview of Database Design Process

Methodologies for Conceptual Design

? Entity Relationship (ER) Diagrams (This

Presentation)

? Enhanced Entity Relationship (EER) Diagrams

? Use of Design Tools

? The UML (Unified Modeling Language) Class

Diagrams

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Example COMPANY Database

? Database Schema Design based on the following (simplified) requirements of the COMPANY Database:

? The company is organized into DEPARTMENTs.

? Each department controls a number of PROJECTs.

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Example COMPANY Database

(Continued)

? The database will store each EMPLOYEE’s social security number, address, salary, sex, and birthdate.

? Each employee may have a number of DEPENDENTs.

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Entity Relationship (ER) Model

Concepts

? Entities and Attributes ? Entity is a basic concept for the ER model.

? Attributes are properties used to describe an entity.

? A specific entity will have a value for each of its attributes.

? Each attribute has a value set (or data type) associated.

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Types of Attributes

? Simple