OMIS-452-SP16 - Week 6b - OMIS 452 Database Management for...

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OMIS 452 Database Management for Business Northern Illinois University Brian Bender
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Agenda Ch. 5 – Entity Relationship Data Model P.3 – Introduction A Look Ahead OMIS-452 Week 6b 2
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Ch. 5 – Entity Relationship Model What Is A Data Model? Plan For Database Design Entity-Relationship (E-R) Model Standard For Database Design Graphical Depiction Of… Entities – Something People Want To Track Tables – Entity Class, Relation Attributes – Characteristics Of Entities Relationships – Association Between Entity Instances Identifiers – A Key By Any Other Name OMIS-452 Week 6b 3
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Ch. 5 – Entity Relationship Model Relationships Can Exist… Between Entity Classes (Tables) Relationship Class Between Entity Instances (Records) Relationship Instance OMIS-452 Week 6b 4
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Ch. 5 – Entity Relationship Model Entity Classes (Tables) Entity Instances (Records) OMIS-452 Week 6b 5
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Ch. 5 – Entity Relationship Model Entity Classes (Tables) Entity Instances (Records) Attributes describe an entity’s characteristics. All entity instances of a given entity class have the same attributes, but vary in the values of those attributes. OMIS-452 Week 6b 6
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Degree of the Relationship The Degree Of The Relationship Is The Number Of Entity Classes In The Relationship: Two Entities Binary Relationship Degree Two Three Entities Ternary Relationship Degree Three OMIS-452 Week 6b 7
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Binary Relationship OMIS-452 Week 6b 8
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Ternary Relationship OMIS-452 Week 6b 9
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Ch. 5 – Entity Relationship Model What Is Cardinality? Count Of The Relationship Minimum – Must Participate Zero (0) = Optional One (1) = Mandatory Maximum Between Relations One-To-One (1:1) One-To-Many (1:N) – Parent Child Many-To-One (N:1) Many-To-Many (N:M) OMIS-452 Week 6b 10
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Three Types of Maximum Cardinality OMIS-452 Week 6b 11
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Three Types of Minimum Cardinality OMIS-452 Week 6b 12
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Ch. 5 – Entity Relationship Model Crow’s Foot Notation ( Required In P.3 ) OMIS-452 Week 6b 13
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One To Many (1:N) OMIS-452 Week 6b 14
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Many To Many (N:M) OMIS-452 Week 6b 15
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Ch. 5 – Entity Relationship Model
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  • Fall '08
  • staff
  • Entity-relationship model, Strong Entity Relationships, Association Between Entity

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