tailieunhanh - Lecture Information systems (3/e): Appendix C - Paige Baltzan

Appendix C - Designing databases. After completing this unit, you should be able to: Describe the purpose of the relational database model in a database management system, list the relational database model’s basic components, describe why entities and attributes are organized into tables and fields, describe how data redundancy is handled in the relational database model. | APPENDIX C DESIGNING DATABASES Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 1 INTRODUCTION The core chapters introduced: Database - maintains information about various types of objects (inventory), events (transactions), people (employees), and places (warehouses) Database management system (DBMS) – creates, reads, updates, and deletes data in a database while controlling access and security Relational database model - a type of database that stores its information in the form of logically-related two-dimensional tables 2 ENTITIES AND DATA RELATIONSHIPS Data model – The logical data structures that detail the relationships among data elements using graphics or pictures The underlying relationships in a database environment are: Independent of the data model Independent of the DBMS that is being used Entity-relationship diagram (ERD) - A technique for documenting the relationships between entities in a database environment 3 Entities And Their Attributes Entity - Also called a table, stores information about a person, place, thing, transaction, or event A customer is an entity, as is a merchandise item Attribute – Data elements associated with an entity A CUSTOMER entity can be described by a Customer Number, First Name, Last Name, Street, City, State, Zip Code, Phone Number 4 Entities And Their Attributes 5 Attributes There are several types of attributes including: Simple versus composite Single-valued versus multi-valued Stored versus derived Null-valued 6 Simple versus Composite Composite attributes can be divided into smaller subparts, which represent more basic attributes that have their own meanings Example: Address Address can be broken down into a number of subparts, such as Street, City, State, Zip Code Street may be further broken down by Number, Street Name, and Apartment/Unit Number Attributes that are not divisible into subparts are called simple | APPENDIX C DESIGNING DATABASES Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 1 INTRODUCTION The core chapters introduced: Database - maintains information about various types of objects (inventory), events (transactions), people (employees), and places (warehouses) Database management system (DBMS) – creates, reads, updates, and deletes data in a database while controlling access and security Relational database model - a type of database that stores its information in the form of logically-related two-dimensional tables 2 ENTITIES AND DATA RELATIONSHIPS Data model – The logical data structures that detail the relationships among data elements using graphics or pictures The underlying relationships in a database environment are: Independent of the data model Independent of the DBMS that is being used Entity-relationship diagram (ERD) - A technique for documenting the .