ERD Exercise

1
ERD Exercise 2

• CIS458
• Organizational Database Management

2
Creating an ERD from the Investigated Facts

• Identify all the entities.
• Identify all the relationships.
• Identify cardinality and multiplicities (min max).

(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.

Displayed
(0..)
(1..1)
Paint ?
?
Painter
Painting
(1,1)
(0..)
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 1000 a.m. to 1050 a.m., and one
  offered on Thursday from 600 p.m. to 840 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