Slide 1 Chapter 05 – Part 2 Data Modeling with the Entity-Relationship Model

Slide 2 Contents A. Sales Order Problem B. Solution

Slide 3 A. Sales Order Problem  A company want to computerize all data. The followings are reports:

Slide 4 Let’s design DB diagram for above requirements

Slide 5 B. Solution 1.Logical Analysis 2.Physical Analysis

Slide 6 1. Logical Analysis 1.1. First solution 1.2. Second solution 1.3. Identify Recursive Relationship

Slide First solution Identify Entity Identify Attribute Identify Weak Entity Identify Primary Identifier Identify Alternative Identifier Identify Mandatory Attribute Identify Relationship

Slide Identify Entity

Slide Identify Attribute

Slide Identify Weak Entity What is Weak Entity? Design using ID-Dependent Entity

Slide What is Weak Entity?  A weak entity is an entity whose existence depends upon another entity.  All ID-Dependent entities are considered weak.  An ID-dependent entity is an entity whose identifier includes the identifier of another entity.  But there are also non-ID-dependent weak entities.  The identifier of the parent does not appear in the identifier of the weak child entity.

Slide Design using ID-Dependent Entity

Slide Identify Primary Identifier

Slide Identify Alternative Identifier

Slide Identify Mandatory Attribute

Slide Identify Relationship Identify Maximum Cardinality Identify Minimum Cardinality

Slide Identify Maximum Cardinality

Slide Identify Minimum Cardinality

Slide Second solution Identify Entity Identify Attribute Identify Primary Identifier Identify Alternative Identifier Identify Mandatory Attribute Identify Relationship

Slide Identify Entity

Slide Identify Attribute

Slide Identify Primary Identifier

Slide Identify Alternative Identifier

Slide Identify Mandatory Attribute

Slide Identify Relationship Identify Maximum Cardinality Identify Minimum Cardinality

Slide Maximum Cardinality on Diagram

Slide Minimum Cardinality on Diagram

Slide Identify Recursive Relationship What is Recursive Relationship? Recursive Relationship on Diagram

Slide What is Recursive Relationship?  A recursive relationship occurs when an entity has a relationship to itself.  There are three types of Recursive Relationships:  1: 1  1:N  N:M

Slide Recursive Relationship on Diagram

Slide Physical Diagram

Slide 32