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 EMPLOYEEs 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
