chapter 3 data modeling l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 3 Data Modeling PowerPoint Presentation
Download Presentation
Chapter 3 Data Modeling

Loading in 2 Seconds...

play fullscreen
1 / 28

Chapter 3 Data Modeling - PowerPoint PPT Presentation


  • 537 Views
  • Uploaded on

Chapter 3 Data Modeling. Fundamentals of Database Management Systems by Mark L. Gillenson, Ph.D. University of Memphis Presentation by: Amita Goyal Chin, Ph.D. Virginia Commonwealth University John Wiley & Sons, Inc. Chapter Objectives.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 3 Data Modeling' - paul


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
chapter 3 data modeling

Chapter 3Data Modeling

Fundamentals of Database Management Systems

by

Mark L. Gillenson, Ph.D.

University of Memphis

Presentation by: Amita Goyal Chin, Ph.D.

Virginia Commonwealth University

John Wiley & Sons, Inc.

chapter objectives
Chapter Objectives
  • Explain the concept and practical use of data modeling.
  • Recognize which relationships in the business environment are unary, binary, and ternary relationships.
  • Describe one-to-one, one-to-many, and many-to-many unary, binary, and ternary relationships.
chapter objectives3
Chapter Objectives
  • Recognize and describe intersection data.
  • Model data in business environments by drawing entity-relationship diagrams that involve unary, binary, and ternary relationships.
essence of data modeling
Essence of Data Modeling
  • Exploring the different ways that entities can relate to each other as they always do in the real world
  • Devising a way of recording, of diagramming, the entities and the ways in which they interrelate in the business environment
entity relationship e r model
Entity-Relationship (E-R) Model
  • A diagramming technique
  • Diagrams entities (with attributes) and the relationship between the entities.
  • There are many variations of E-R diagrams in use.
e r model entity and its attributes
E-R Model Entity (and its attributes)
  • Rectangular shape
  • Salesperson = a type of entity
  • Name of entity is in caps above the separator line.
e r model entity and its attributes7
E-R Model Entity (and its attributes)
  • Entity type’s attributes are shown below the separator line.
  • An asterisk denotes attribute(s) that constitute the entity type’s unique identifier.
relationships
Relationships
  • Associations between entities
  • Different kinds:
    • Binary relationships
    • Unary relationships
    • Ternary relationships
binary relationships
Binary Relationships
  • Simplest kind of relationship
  • Relationship between two entity types
  • Diamond-shaped box represents relationship
  • A salesperson “sells” products or products are sold by salespersons
cardinality
Cardinality
  • Represents the maximum number of entities that can be involved in a particular relationship.
    • One-to-One Binary Relationship
    • One-to-Many Binary Relationship
    • Many-to-Many Binary Relationship
one to one binary relationship
One-to-One Binary Relationship
  • 1-1
  • A single occurrence of one entity type can be associated with a single occurrence of the other entity type and vice versa.
one to many binary relationship
One-to-Many Binary Relationship
  • 1-M
  • Use “crow’s foot” to represent the multiple association.
  • “many” = the maximum number of occurrences that can be involved, means a number that can be 1, 2, 3, ... n.
many to many binary relationship
Many-to-Many Binary Relationship
  • M-M
  • “many” can be either an exact number or have a known maximum.
modality
Modality
  • The minimum number of entity occurrences that can be involved in a relationship.
  • “inner” symbol on E-R diagram (“outer” symbol is cardinality)
intersection data
Intersection Data
  • Describes the relationship between two entities.
  • Used with many-to-many relationships.
  • Represented on E-R diagram in a special five-sided intersection data box, which is attached to the relationship diamond between the two entity boxes.
many to many binary relationship with intersection data
Many-to-Many Binary Relationship with Intersection Data
  • For example, we know not only that salesperson 137 sold some of product 24013 but also how many units of that product that salesperson sold.
associative entity
Associative Entity
  • Entities can have attributes; many-to-many relationships can have attributes.
  • Many-to-many relationship may be treated similarly to entities in an E-R diagram.
associative entity20
Associative Entity
  • Should you diagram as associative entity or many-to-many relationship?
    • personal taste
    • follow company standards
  • The unique identifier of the associative entity is usually the combination of the unique identifiers of the two entities in the many-to-many relationship.
unary relationships
Unary Relationships
  • Associate occurrences of an entity type with other occurrences of the same entity type.
  • Cardinality:
    • One-to-One Unary Relationship
    • One-to-Many Unary Relationship
    • Many-to-Many Unary Relationship
ternary relationship
Ternary Relationship
  • Involves three different entity types.
slide24
Ternary Relationship: The General Hardware Company E-R Diagram
  • Customer Employee, a dependent entity, is distinguished by a diagonal hash mark in each corner of its attribute area.
slide28

“Copyright 2004 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 express 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 back-up 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.”