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Chapter 05 – Part 2Data Modeling with the

Entity-Relationship Model

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ContentsA. Sales Order ProblemB. Solution

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A. Sales Order Problem A company want to computerize all data. The

followings are reports:

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Let’s design DB diagram for above requirements

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B. Solution1. Logical Analysis2. Physical Analysis

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1. Logical Analysis1.1. First solution1.2. Second solution1.3. Identify Recursive Relationship

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1.1. First solution1.1.1. Identify Entity1.1.2. Identify Attribute1.1.3. Identify Weak Entity1.1.4. Identify Primary Identifier1.1.5. Identify Alternative Identifier1.1.6. Identify Mandatory Attribute1.1.7. Identify Relationship

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1.1.1. Identify Entity

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1.1.2. Identify Attribute

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1.1.3. Identify Weak Entity1.1.3.1. What is Weak Entity?1.1.3.2. Design using ID-Dependent Entity

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1.1.3.1. 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.

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1.1.3.2. Design using ID-Dependent Entity

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1.1.4. Identify Primary Identifier

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1.1.5. Identify Alternative Identifier

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1.1.6. Identify Mandatory Attribute

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1.1.7. Identify Relationship1.1.7.1. Identify Maximum Cardinality1.1.7.2. Identify Minimum Cardinality

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1.1.7.1. Identify Maximum Cardinality

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1.1.7.2. Identify Minimum Cardinality

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1.2. Second solution1.2.1. Identify Entity1.2.2. Identify Attribute1.2.3. Identify Primary Identifier1.2.4. Identify Alternative Identifier1.2.5. Identify Mandatory Attribute1.2.6. Identify Relationship

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1.2.1. Identify Entity

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1.2.2. Identify Attribute

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1.2.3. Identify Primary Identifier

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1.2.4. Identify Alternative Identifier

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1.2.5. Identify Mandatory Attribute

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1.2.6. Identify Relationship1.2.6.1. Identify Maximum Cardinality1.2.6.2. Identify Minimum Cardinality

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1.2.6.1 Maximum Cardinality on Diagram

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1.2.6.2. Minimum Cardinality on Diagram

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1.3. Identify Recursive Relationship

1.3.1. What is Recursive Relationship?1.3.2. Recursive Relationship on Diagram

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1.3.1. 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

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1.3.2. Recursive Relationship on Diagram

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2. Physical Diagram

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