Chapter 7 - Entity-relationship model. This chapter provides an overview of the database-design process, with major emphasis on database design using the entity-relationship data model. The entity-relationship data model provides a high-level view of the issues in database design, and of the problems that we encounter in capturing the semantics of realistic applications within the constraints of a data model. UML class-diagram notation is also covered in this chapter. | Chapter 7: Entity-Relationship Model Database System Concepts, 6th Ed. ©Silberschatz, Korth and Sudarshan See for conditions on re-use Chapter 7: Entity-Relationship Model Design Process Modeling Constraints E-R Diagram Design Issues Weak Entity Sets Extended E-R Features Design of the Bank Database Reduction to Relation Schemas Database Design UML Database System Concepts - 6th Edition ©Silberschatz, Korth and Sudarshan Modeling A database can be modeled as: a collection of entities, relationship among entities. An entity is an object that exists and is distinguishable from other objects. Example: specific person, company, event, plant Entities have attributes Example: people have names and addresses An entity set is a set of entities of the same type that share the same properties. Example: set of all persons, companies, trees, holidays Database System Concepts - 6th Edition ©Silberschatz, Korth and Sudarshan Entity Sets instructor and student instructor_ID instructor_name Database System Concepts - 6th Edition student-ID student_name ©Silberschatz, Korth and Sudarshan Relationship Sets A relationship is an association among several entities Example: 44553 (Peltier) student entity advisor relationship set 22222 (Einstein) instructor entity A relationship set is a mathematical relation among n ≥ 2 entities, each taken from entity sets {(e1, e2, en) | e1 ∈ E1, e2 ∈ E2, , en ∈ En} where (e1, e2, , en) is a relationship Example: (44553,22222) ∈ advisor Database System Concepts - 6th Edition ©Silberschatz, Korth and .
