Transcript Chapter 3
Chapter 3: Data Modeling Introduction An Overview of Databases Steps in Developing a Database Using Resources, Events and Agents Model Normalization Chapter 3-1 Introduction Uses of a modern AIS Systematically Provide Easy record data convenient and useful formats access to information Chapter 3-2 What is a Database? Collection of organized data Used by many different computer applications Manipulated by database management systems (DBMS) Chapter 3-3 Significance of a Database Critical information Volume Distribution Privacy Irreplaceable data Need for accuracy Internet uses Chapter 3-4 Storing Data in Databases Data must be stored and organized systematically Three important concepts: Data hierarchy Record structures Database keys Chapter 3-5 Data Hierarchy Data organization in ascending order: Data field Record File Database Chapter 3-6 Record Structures Data fields in each record of a database table Structure is usually fixed Example Chapter 3-7 Database Keys Primary Key Unique to each record Foreign Keys Enable referencing of one or more records Matches primary key of related table Chapter 3-8 Records Combined Into Report Chapter 3-9 Additional Database Issues Administration Database Administrator Documentation Includes a variety of descriptions Structures, Contents, Security Features Data Dictionary Metadata Chapter 3-10 Data Dictionary Example Chapter 3-11 Additional Database Issues Data Integrity Data Integrity controls Designed by database developers Processing Accuracy and Completeness Transaction controls Ensures accurate transaction processing Chapter 3-12 Additional Database Issues Concurrency Concurrency controls Prevent multi-user access at same time Backup and Security Ability to recreate data Prevent unauthorized access View controls Chapter 3-13 Study Break #1 The part of the data hierarchy that represents one instance of an entity is a: A. Field B. Record C. File D. Database Chapter 3-14 Study Break #1 - Answer The part of the data hierarchy that represents one instance of an entity is a: A. Field B. Record C. File D. Database Chapter 3-15 Study Break #2 Within the context of databases, the term “concurrency” refers to the possibility that: A. A customer of one store might also be a customer of another store B. Two database users might want to access the same record at the same time C. A credit entry for a customer requires a debit entry for a matching account D. None of these Chapter 3-16 Study Break #2 - Answer Within the context of databases, the term “concurrency” refers to the possibility that: A. A customer of one store might also be a customer of another store B. Two database users might want to access the same record at the same time C. A credit entry for a customer requires a debit entry for a matching account D. None of these Chapter 3-17 REA Model Resources Organization’s assets Events Activities associated with a business processes Agents People associated with business activities Chapter 3-18 Steps in Developing Databases with REA Identify Business and Economic Events Identify Entities Identify Relationships Among Entities Chapter 3-19 Steps in Developing Databases with REA Create Entity-Relationship Diagrams Identify Attributes of Entities Convert E-R Diagrams into Database Tables Chapter 3-20 Identify Events and Entities Types of Events Business Economic Types of Database Entities Entities Agents Resources Chapter 3-21 Entity Examples Chapter 3-22 Identify Relationships Among Entities Types of Relationships Direct relationship Indirect relationship Cardinalities Nature of relationships among entities Chapter 3-23 Cardinality Relationships Notations One-to-one (1:1) One-to-many (1:N) Many-to-many (N:N) Purpose Occurrence of one entity Associated with occurrence of one event of another entity Chapter 3-24 Cardinality Relationships Chapter 3-25 Entity-Relationship Diagram Purpose Diagram entities Relationships among entities Structure Rectangles represent entities Connecting lines represent relationships Chapter 3-26 E-R Diagram Example Chapter 3-27 Relationship Tables Provide greater flexibility Need for Relationship Tables Linking tables with foreign keys Many-to-many relationships Chapter 3-28 Relationship Tables Chapter 3-29 Schematic of Database Tables Chapter 3-30 Study Break #3 In the REA model, the “A” stands for: A. Agents B. Additions C. Accounts D. Associations Chapter 3-31 Study Break #3 - Answer In the REA model, the “A” stands for: A. Agents B. Additions C. Accounts D. Associations Chapter 3-32 Study Break #4 Which of these is not a cardinality between two database entities? A. One-to-one B. None-to-none C. One-to-many D. Many-to-many Chapter 3-33 Study Break #4 - Answer Which of these is not a cardinality between two database entities? A. One-to-one B. None-to-none C. One-to-many D. Many-to-many Chapter 3-34 Normalization Normalization Methodology ensuring attributes are stored in most appropriate tables Design promotes accuracy Avoids redundancy of data storage Levels First normal form Second normal form Third normal form Chapter 3-35 Unnormalized Data Chapter 3-36 First Normal Form In First Normal Form (1 NF) when: All data fields are singular Each attribute has one value Problems Data redundancy Insertion anomaly Deletion anomaly Chapter 3-37 First Normal Form Example Chapter 3-38 Second Normal Form In Second Normal Form (2 NF) when: It is in 1 NF All data items depend on primary record key Benefits More efficient design Eliminates data redundancy Chapter 3-39 Second Normal Form Example Chapter 3-40 Third Normal Form In Third Normal Form (3 NF) when: It is in 2 NF Does not contain transitive dependencies Data field A does not determine data field B Ultimate Goal Create database in 3 NF Chapter 3-41 Third Normal Form Example Chapter 3-42 Study Break #5 A database is in third normal form (3NF) if it is second normal form and: A. All the data attributes in a record are well defined B. All the data attributes in a record depend on the record key C. The data contain to transitive dependencies D. The data can be stored in two or more separate tables Chapter 3-43 Study Break #5 - Answer A database is in third normal form (3NF) if it is second normal form and: A. All the data attributes in a record are well defined B. All the data attributes in a record depend on the record key C. The data contain to transitive dependencies D. The data can be stored in two or more separate tables Chapter 3-44 Copyright Copyright 2012 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make backup copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein. Chapter 3-45 Chapter 3 Chapter 3-46