MGMT 360 Database Management

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MGMT 360Database Management

• Data Modeling

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Outline

• Notation basics
• Understanding relationships
• Generalization hierarchies
• Problem solving strategies

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Basic Symbols
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Cardinalities
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Cardinality Notation
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Classification of Cardinalities

• Minimum cardinality based
• Mandatory
• Optional
• Maximum cardinality based
• Functional
• 1-M
• M-N
• 1-1

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More Relationship Examples
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Comparison to Access Notation
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Understanding Relationships

• Identification dependency
• M-N relationships with attributes
• Self-identifying relationships
• M-way relationships
• Equivalence between M-N and 1-M relationships

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Identification Dependency
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M-N Relationships with Attributes
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Instance Diagrams for Self-Referencing
Relationships
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ERD Notation for Self-Referencing Relationships
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Associative Entity Types for M-way Relationships
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Associative Entity Types for M-way Relationships
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Associative Entity Types for M-way Relationships
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Associative Entity Types
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Associative Entity Types
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Relationship Equivalence

• Replace M-N relationship
• Associative entity type
• Two identifying 1-M relationships
• M-N relationship versus associative entity type
• Largely preference
• Associative entity more flexible in some
  situations

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Associative Entity Type Example
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Generalization Hierarchies
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Inheritance

• Subtypes inherit attributes of supertypes (direct
  and indirect)
• Allows abbreviation of attribute list
• Applies to code (methods) as well as attributes
  (data)

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Generalization Constraints
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Multiple Levels of Generalization
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Problem Solving Strategies

• Use notation precisely
• Strive for simplicity
• ERD connections
• Avoid over connecting the ERD
• Identify hub(s) of the ERD
• Use specialized patterns carefully
• Justify important design decisions

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Common Notation Errors

• Identifying versus non-identifying relationships
• Unique relationship names
• Cardinality for weak entities
• Usage of foreign keys

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Attribute to Entity Type Transformation
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Compound Attribute Transformation
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Generalization Hierarchy Transformation
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Entity Type Expansion Transformation
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Summary

• Data modeling is an important skill
• No standard ERD notation
• Use notation precisely
• Apply specialized concepts carefully
• Work many problems