Chapter 3 The Entity-Relationship Model David M. Kroenke Database Processing © 2000 Prentice Hall

Chapter 3 © 2000 Prentice Hall Data Modeling Page 47 Process of creating a logical representation of the structure of the database The most important task in database development

Chapter 3 © 2000 Prentice Hall Entity-Relationship Model E-R Model Peter Chen, 1976 Page 49

Entities “something that users track” Page 49 Figure 3-1 © 2000 Prentice Hall

Chapter 3 © 2000 Prentice Hall Attributes (properties) “describe the entity’s characteristics” Entity:Employee Attributes:EmployeeName, Extension, DateOfHire, JobSkillCode Page 50

Chapter 3 © 2000 Prentice Hall Identifier “attributes that name entity instances” Entity:Employee Identifier:SocialSecurityNumber Page 50

Relationships “associations between entities” Page 51 Figure 3-3 © 2000 Prentice Hall

Cardinality “maximum or minimum number of entities that can occur on one side of a relationship” Page 52 Figure 3-4 © 2000 Prentice Hall

Recursive relationships “relationships among entities of a single class” Page 53 Figure 3-5 © 2000 Prentice Hall

E-R Diagram Page 54 Figure 3-6a © 2000 Prentice Hall

E-R Diagram Page 54 Figure 3-6b © 2000 Prentice Hall

Chapter 3 © 2000 Prentice Hall Weak Entities “an entity whose presence in the database depends (logically) on another entity” Page 54

Subtype Entities “an entity that contains option sets of attributes” Page 56 Figure 3-10b © 2000 Prentice Hall

E-R Diagram with all elements Page 59 Figure 3-11 © 2000 Prentice Hall

Chapter 3 © 2000 Prentice Hall Drawing E-R diagrams IEW IEF DEFT ER-WIN Visio Page 60

Jefferson Dance Club Page 62 Figure 3-14 © 2000 Prentice Hall

San Juan Charters Page 66 Figure 3-16 © 2000 Prentice Hall