Amplified E-R Model: Basic Symbols

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Expanded E-R: Relationship Cardinality. Compulsory One. Obligatory Many. Discretionary One. Discretionary Many. . . . . . . . . Relationship Set: Cardinality. . . . . Most extreme Cardinality for Course. Most extreme Cardinality for Offering. Least Cardinality for Course. Least Cardinality for Offering. Course. Course-NOC-DesCredit-Hour.

Presentation Transcript

Slide 1

´╗┐Expanded E-R Model: Basic Symbols Strong Entity Set Associative Entity Set Weak Entity Set Attribute Association Relationship Set Multi-Valued Attribute Identifying Relationship Set Derived trait

Slide 2

Extended E-R: Relationship Cardinality Mandatory One Mandatory Many Optional One Optional Many

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Relationship Set: Cardinality Maximum Cardinality for Offering Maximum Cardinality for Course Has Offering (1:1) (0:N) Course-NO C-Des Credit-Hour Offer-NO Off-Location Off-Time Minimum Cardinality for Offering Minimum Cardinality for Course

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EMPLYEE 1: One M: Many DEPARTMENT Works-for 1 M Works-for EMPLOYEE DEPARTMENT Many One Graphical Notations for Cardinality : One EMPLOYEE DEPARTMENT Works-for : Many : One : Many EMPLOYEE DEPARTMENT Works-for

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ER Diagram: An Example Sends SUPPLIER Supplies CUSTOMER Includes SHIPMENT ITEM Submits KEY Relationship Used_in Entity Cardinalities Mandatory One Requests PRODUCT ORDER Mandatory Many Optional One Optional Many

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DEPENDENT Has EMPLOYEE Weak Entity: An Example Last_Name First_Name Middle_Initial Date_of_Birth Employee_Name Employee_ID Dependent_Name

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Unary Relationship: Examples Marries PERSON One-to-one Manages EMPLOYEE One-to-numerous

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Binary Relationship: Examples EMPLOYEE Assigns PARKING PLACE One-to-One PRODUCT LINE Contains PRODUCT One-to-Many STUDENT Registers_for COURSE Many-to-Many

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PART Supplies VENDOR WAREHOUSE Unit_cost Shipping_mode Ternary Relationships: Example

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Address City Postal_Code Street_Address State Composite Attribute DB Design Question: Should we show address as a basic or composite quality?

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Employee_Name Employee_ID Address Years_Employed Skill EMPLOYEE Date_Employed Multi-Valued versus Derived Attribute

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Specialization/Generalization Relationships: Disjointness and Completeness Constraints PERSON Overlapping and Partial Coverage IS-An (O,P) DOCTOR PATIENT Disjoint and Total Coverage IS-A (D,T) IN-PATIENT OUT-PATIENT

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