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# ERD Exercise #2 PowerPoint PPT Presentation

ERD Exercise #2 CIS458 Organizational Database Management 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) Simple ERD 1

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ERD Exercise #2

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## ERD Exercise #2

CIS458

Organizational Database Management

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)

### 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

### 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

### Simple ERD 3

• An employee manages one store; each store is managed by one employee

Employee

Store

Manages ►

(0..1)

(1..1)

Employee

Store

### 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.

Has ►

(1..1)

(0..*)

Course

Section

### Simple ERD 5

• Each student can take many classes (or no class at all) and each class can contain many students.

Take ►

(1..*)

(0..*)

Student

Classes

### Combining ERDs

• A class can be identified with course and section.

Has ►

(1..1)

(0..*)

Course

Section

Take ►

(1..*)

(0..*)

Student

Section

Has ►

(1..1)

(0..*)

Course

Section

(0..*)

Take▼

(1..*)

Student

Has ►

(1..1)

(0..*)

Course

Section

(0..*)

(0..*)

(0..*)

Take ▼