Using MIS (9th Edition)
Using MIS (9th Edition)
9th Edition
ISBN: 9780134106786
Author: David M. Kroenke, Randall J. Boyle
Publisher: PEARSON
Question
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Chapter 5, Problem 5.6CE5
Program Plan Intro

E-R model:

  • E-R model is a tool for creating data model.
  • It is used for developers to describe the content of data model by using two functions called entities and relationships.

Entity:

  • Entity helps the user for tracking something in database.
  • Example entities in student database system are Student, Grade, Course, etc.

Relationships:

  • Entities have relationships among each other.
  • For example, in student database, a Student has a relationship to Major and Student has a relationship to Advisor.

Maximum cardinality:

Maximum cardinality is referred as maximum number of entities that are involved in a relationship.

The three examples of maximum cardinality are:

  • l:N(one to Many relationship)
  • 1:1(one to one relationship)
  • N:M(Many to many relationship)

Minimum cardinality:

  • It gives the minimum number of entities that are required for relationship.
  • Controls on minimum requirements are referred as minimum cardinality.

The two examples of minimum cardinality are:

  • It could contain 0 relationship
  • It could contain 1 relationship

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