Đang chuẩn bị liên kết để tải về tài liệu:
Lecture Database concepts (3rd Edition): Chapter 4 - David M. Kroenke, David J. Auer

Chapter 4 - Data modeling and the entity-relationship model. In this chapter students will be able to: Learn the basic stages of database development, understand the purpose and role of a data model, know the principal components of the E-R data model, understand how to interpret traditional E-R diagrams, understand how to interpret Information Engineering (IE) Crow’s Foot E-R diagrams, | Data Modeling and the Entity-Relationship Model Chapter Four DAVID M. KROENKE and DAVID J. AUER DATABASE CONCEPTS, 3rd Edition Chapter Objectives Learn the basic stages of database development Understand the purpose and role of a data model Know the principal components of the E-R data model Understand how to interpret traditional E-R diagrams Understand how to interpret Information Engineering (IE) Crow’s Foot E-R diagrams Learn to construct E-R diagrams Know how to represent 1:1, 1:N, N:M, and binary relationships with the E-R model 4- Chapter Objectives (Continued) Understand two types of weak entities and know how to use them Understand nonidentifying and identifying relationships and know how to use them Know how to represent subtype entities with the E-R model Know how to represent recursive relationships with the E-R model Learn how to create an E-R diagram from source documents 4- Three Stages of Database Development Requirements Stage Design Stage Implementation Stage 4- The Requirements Stage Sources of requirements User Interviews Forms Reports Queries Use Cases Business Rules 4- Requirements Become the E-R Data Model After the requirements have been gathered, they are transformed into an Entity Relationship (E-R) Data Model E-R Models consist of Entities Attributes Identifiers Relationships 4- Entity Class versus Entity Instance An entity class is a description of the structure and format of the occurrences of the entity An entity instance of a specific occurrence of an entity class 4- Entity Class and Entity Instance 4- Attributes Entities have attributes that describe the entity’s characteristics ProjectName StartDate ProjectType ProjectDescription Attributes have a data type and properties 4- Identifiers Entity instances have identifiers An identifier will identify a particular instance in the entity class SocialSecurityNumber StudentID EmployeeID 4- Identifier Types Uniqueness Identifiers may be unique or . | Data Modeling and the Entity-Relationship Model Chapter Four DAVID M. KROENKE and DAVID J. AUER DATABASE CONCEPTS, 3rd Edition Chapter Objectives Learn the basic stages of database development Understand the purpose and role of a data model Know the principal components of the E-R data model Understand how to interpret traditional E-R diagrams Understand how to interpret Information Engineering (IE) Crow’s Foot E-R diagrams Learn to construct E-R diagrams Know how to represent 1:1, 1:N, N:M, and binary relationships with the E-R model 4- Chapter Objectives (Continued) Understand two types of weak entities and know how to use them Understand nonidentifying and identifying relationships and know how to use them Know how to represent subtype entities with the E-R model Know how to represent recursive relationships with the E-R model Learn how to create an E-R diagram from source documents 4- Three Stages of Database Development Requirements Stage Design Stage Implementation Stage