TAILIEUCHUNG - Lecture Enterprise systems development - Lecture 26

After studying this chapter you will be able to: Identify how databases and spreadsheets are both similar and different; list and describe the four steps in designing and building a relational database; define the concepts of entity class, instance, primary key, and foreign key; given a small operating environment, build an entity-relationship (E-R) diagram. | Lecture 26 Enterprise Systems Development ( CSC447) COMSATS Islamabad Muhammad Usman, Assistant Professor College of Statistical and Acturial Science Entity-Relationship Model 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 Entity Sets customer and loan customer_id customer_ customer_ customer_ loan_ amount name street city number Relationship Sets A relationship is an association among several entities Example: Hayes depositor A-102 customer entity relationship set account entity A relationship set is a mathematical relation among n 2 entities, each taken from entity sets {(e1, e2, en)

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