ERD Exercise #2 - PowerPoint PPT Presentation

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ERD Exercise #2

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  1. ERD Exercise #2 CIS458 Organizational Database Management

  2. Identify all the entities. Identify all the relationships. Identify cardinality and multiplicities (min max). Creating an ERD from the Investigated Facts (1..*) (0..1) (0..*) (1..1)

  3. Simple ERD 1 • A painter can paint many paintings; each paining is painted by one painter. A gallery can have many paintings. A painting can be exhibited by a gallery. Paint ► (0..*) Displayed (1..1) ► Painter (1,1) (0..*) Painting Gallery

  4. Simple ERD 2 • An employee can learn many skills; each skill can be learned by many employees. • Expert Level? (L1.. L5) Learn ► (0..*) (0..*) Employee Skills Expert Level

  5. Simple ERD 3 • An employee manages one store; each store is managed by one employee Employee Store Manages ► (0..1) (1..1) Employee Store

  6. Simple ERD 4 • A College example • Students in a typical college or university will discover that each course can have many sections or no section, by each section refers to only one course. • For example, an Accounting II course might have two sections: one offered on Monday, Wednesday, and Friday from 10:00 a.m. to 10:50 a.m., and one offered on Thursday from 6:00 p.m. to 8:40 p.m.

  7. Has ► (1..1) (0..*) Course Section

  8. Simple ERD 5 • Each student can take many classes (or no class at all) and each class can contain many students. • Add Grade Take ► (1..*) (0..*) Student Classes Grade

  9. Combining ERDs • A class can be identified with course and section. Has ► (1..1) (0..*) Course Section Take ► (1..*) (0..*) Student Section

  10. Has ► (1..1) (0..*) Course Section (0..*) Take▼ (1..*) Student

  11. Adding Additional Conditions • Adding prerequisite, enroll grade Has ► (1..1) (0..*) Course Section (0..*) (0..*) (0..*) Take ▼ Grade ◄Prerequisite (1..*) Student