Chapter 4 - Chapter4:EntityRelationshipModeling How...

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Chapter 4: Entity Relationship Modeling How relationships between entities are defined and refined, and how such relationships are incorporated into the database design process How ERD components affect database design and implementation How to interpret the modeling symbols for the four most popular ER modeling tools That real-world database design often requires that you reconcile conflicting goals Entity Relationship Model and Diagram ER model forms the basis of an ER diagram ERD represents the conceptual database as viewed by end user ERDs depict the ER model’s three main components: o Entities o Attributes o Relationships Several different diagramming conventions Entities Refers to the entity set and not to a single entity occurrence Corresponds to a table and not to a row in the relational environment In both the Chen and Crow’s Foot models, an entity is represented by a rectangle containing the entity’s name Entity name, a noun, is usually written in capital letters Attributes Characteristics of entities Domain is set of possible values Primary keys underlined
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Attributes (cont) Attributes (cont) Simple Cannot be subdivided Age, sex, GPA
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This note was uploaded on 10/25/2010 for the course CMPN SEM4 taught by Professor Thakur during the Spring '07 term at University of Mumbai.

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Chapter 4 - Chapter4:EntityRelationshipModeling How...

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