Đang chuẩn bị liên kết để tải về tài liệu:
Lecture Database design, application development and administration - Chapter 5: Understanding entity relationship diagrams

Chapter 5 - Understanding entity relationship diagrams. Chapter 2 provided a broad presentation about the database development process. You learned about the relationship between database development and information systems development, the phases of database development, and the kinds of skills you need to master. This chapter presents the notation of entity relationship diagrams to provide a foundation for using entity relationship diagrams in the database development process. | Chapter 5 Understanding Entity Relationship Diagrams Welcome to Chapter 5 on Understanding Entity Relationship Models: - First data modeling chapter - Focused on the notation (syntax) not on the application of the ERD notation - Chapter 6 emphasizes application of the notation - Important skill for database development: data modeling - Data modeling is challenging - Ambiguity: part science, part art - Opportunity for some creative problem solving Objectives: understand notation - Entity types, relationships, attributes - Cardinalities - Relationship patterns - Generalization hierarchies - Representation of business rules in an ERD - Use notation to precisely - Construct diagrams without notational errors - Detect notational errors - Explore CASE tools: ER Assistant Outline Notation basics Understanding relationships Generalization hierarchies Business rule representation Diagram rules Alternative notations Basic notation: - Entities - Relationships - Cardinalities Understanding relationships: - Identification dependency - M-N relationships with attributes - Self-referencing relationships - M-way relationships - Equivalence between M-N relationships and 1-M relationships Generalization hierarchies: - Notation: supertypes and subtypes, inheritance - When to use Representation of business rules Formally in an ERD Informally in associated documentation Diagram rules: - Completeness rules - Consistency rules - Support in the ER Assistant Basic Symbols Entity type: - Collection of things of interest: persons, places, things, events - Contains attributes: like columns - Primary key - Entity: instance or member of an entity type Relationship: - Named association among entities: name is significant (gives it more status) - Similar to a foreign key in relational model except for name and cardinalities - Usually between two entity types: can involve multiple entity types and one - Bidirectional: - Can be used to navigate in both directions - Two names - Course to Offering: . | Chapter 5 Understanding Entity Relationship Diagrams Welcome to Chapter 5 on Understanding Entity Relationship Models: - First data modeling chapter - Focused on the notation (syntax) not on the application of the ERD notation - Chapter 6 emphasizes application of the notation - Important skill for database development: data modeling - Data modeling is challenging - Ambiguity: part science, part art - Opportunity for some creative problem solving Objectives: understand notation - Entity types, relationships, attributes - Cardinalities - Relationship patterns - Generalization hierarchies - Representation of business rules in an ERD - Use notation to precisely - Construct diagrams without notational errors - Detect notational errors - Explore CASE tools: ER Assistant Outline Notation basics Understanding relationships Generalization hierarchies Business rule representation Diagram rules Alternative notations Basic notation: - Entities - Relationships - Cardinalities Understanding .