1. Database Management System
Chapter 4-2
ER Diagram (Cont.)
Adisak Intana
Lecturer
ER Diagram

2. Tranform E-R Diagram to Relation
One-to-one relationship
Key2
Key1 R1
Entity2
Entity1
OR:
Entity1(Key1, … , Key2)
Entity2(Key2, … )
Relation:
Entity1(Key1, … )
Entity2(Key2, … , Key1)
ER Diagram

3. Tranform E-R Diagram to Relation
Example
PK#
Em#
assign
Parking Place
Employee
Relation:
Employee(EM#, … )
ParkingPlace(PK#, … , EM#)
OR:
Entity1(EM#, … , PK#)
Entity2(PK#, … )
ER Diagram

4. Tranform E-R Diagram to Relation
One-to-Many Relationship
Key2
Key1 1 R1 M
Entity2
Entity1
Relation:
Entity1(Key1, … )
Entity2(Key2, … , Key1)
ER Diagram

5. Tranform E-R Diagram to Relation
Many-to-One relationship
Key2
Key1 M R1 1
Entity2
Entity1
Relation:
Entity1(Key1, … , Key2)
Entity2(Key2, … )
ER Diagram

6. Tranform E-R Diagram to Relation
One-to-many relationship T#
ST# 1 M R1
Advisor
Student
Relation:
Student(ST1, … , T#)
Advisor(T#, … )
ER Diagram

7. Tranform E-R Diagram to Relation
Many-to-Many relationship
Key2
Key1 M R1 N
Entity2
Entity1
Relation:
Entity1(Key1, …) R1(Key1,Key2,…)
Entity2(Key2, … )
ER Diagram

8. Tranform E-R Diagram to Relation
Many-to-Many relationship
Sub#
ST# M
Regist N
Subject
Student
Relation:
Student(ST#, …) Regist(ST#,Sub#,…)
Subject(Sub#, … )
ER Diagram