1. Relational Database Design
TOPIC 3 (part 1)
Relational Database Design
(Top Down)
Dr. WENNY RAHAYU
Readings : Chpts 3 & 7, Elmasri & Navathe

2. Relational Database Design
Two Approaches in Relational Database Design
-- From Data Modeling ( eg. ER Model to Relational Logical Model
for implementation.
TOP DOWN DESIGN
-- Normalization of Relations
BOTTOM UP DESIGN
Today’s lecture looks at top-down design, bottom-up design will be described the next lecture
Topic 3 : Relational Database Design

3. Relational Database Design
Consider the following ER-Diagram
manages
empNo
deptNo
name
deptName
1 (1, 1)
1 (0, 1)
address
Department
Employee
M (1, 1)
degree
1 (0, m)
M (1, m)
works for
1 (1, m)
has
works on
projNo
M (1, 1)
M (1, m)
projName
Dependent
Project
dependentName
M (0, m)
dateOfBirth
partNo
supplies
partName
M (1, m)
M (1, m)
Supplier
Part
quantity
supNo
supName
date
Topic 3 : Relational Database Design

4. Relational Database Design
(1) Transformation of E-R Model into Relational Logical Model ( Top Down design )
-- E-R to Relational Mapping Algorithm will be explained here step by step.
STEP 1: For each entity in the ER model, create a relation ( i.e a table that
includes all the simple attributes). Make sure to identify the primary key for
the relation (i.e the PK of the entity).
Note: if there is a specialization/generalization relationship in your EER
(to be discussed in Topic 3- part 2, you need to transform the ‘superclass’ entity
only within this Step 1).
Taking the ER-Diagram on the previous slide as an example:
EMPLOYEE (empNo, name, address)
DEPARTMENT(deptNo, deptName)
PROJECT(projNo, projTitle)
SUPPLIER(supNo, supName)
PART(partNo, partName)
Topic 3 : Relational Database Design

5. Relational Database Design
Transformation of E-R Model into Relational Logical Model ( Top Down design )
STEP 2: For each weak entity in the ER model, create a relation which
includes all the simple attributes. The primary key of the relation is the
combination of the primary key/s of the ‘owner’ and the the key of the
weak entity itself.
Employee
empNo
name
address
Dependent
has
dependentName
dateOfBirth
degree
1 (0, m)
M (1, 1)
DEPENDENT( empNo, dependentName, dateOfBirth)
Topic 3 : Relational Database Design

6. Relational Database Design
Transformation of E-R Model into Relational Logical Model ( Top Down design )
STEP 3: For each binary 1 TO 1 Relationship identify the two relations that
correspond to the entities participating in the relationship. Choose one of
the Relation ( usually the one with total participation) and include as foreign
key the primary key of the the other relation.
Employee
Department
manages
empNo
name
address
deptNo
deptName
degree
1 (0, 1)
1 (1, 1)
DEPARTMENT( deptNo, deptName, mngrEmpNo)
Topic 3 : Relational Database Design

7. Relational Database Design
Transformation of E-R Model into Relational Logical Model ( Top Down design )
STEP4: For each binary 1 TO N Relationship identify the relations that
represent the participating entity at the N (i.e many) side of the relationship.
Include as foreign key in the relation that holds the N side, the primary key
of the other entity (that holds the 1 side)
Employee
Department
works for
empNo
name
address
deptNo
deptName
degree
1 (1, m)
M (1, 1)
EMPLOYEE (empNo, name, address, deptNo)
Topic 3 : Relational Database Design

8. Relational Database Design
Transformation of E-R Model into Relational Logical Model ( Top Down design )
STEP 5: For each binary M:N Relationship create a new relation to represent
the relationship. The primary key of the new relation is the combination of
the primary keys of the two connected entities.
Employee
Project
works on
empNo
name
address
degree
projNo
projName
M (1, m)
WORKS ON (empNo, projNo)
Topic 3 : Relational Database Design

9. Relational Database Design
Transformation of E-R Model into Relational Logical Model ( Top Down design )
STEP 6: For each multivalued attribute, create a new relation that includes
the multivalued attribute and the primary key of the entity where the
multivalued attribute is attached.
Employee
empNo
name
address
degree
EMPLOYEE (empNo, name, address)
EDEGREE(empNo, degree)
Topic 3 : Relational Database Design

10. Relational Database Design
Transformation of E-R Model into Relational Logical Model ( Top Down design )
STEP 7: For each n-ary ( > 2 ) Relationship create a new relation to represent
the relationship. The primary key of the new relation is the combination of the
primary keys of the participating entities that hold the N (many) side. In most
cases of an n-ary relationship all the participating entities hold a many side.
Project
Supplier
Part
supplies
supNo
supName
quantity
date
partNo
partName
projNo
projName
M (1, m)
M (0, m)
SUPPLIES (supNo , projNo, partNo , date, quantity)
Topic 3: Relational Database Design

11. Final Tables PROJECT(projNo, projTitle) SUPPLIER(supNo, supName)
Relational Database Design
Final Tables
PROJECT(projNo, projTitle)
SUPPLIER(supNo, supName)
PART(partNo, partName)
DEPENDENT( empNo, dependentName, dateOfBirth)
DEPARTMENT( deptNo, deptName, mngrEmpNo)
EMPLOYEE (empNo, name, address, deptNo)
WORKS ON (empNo, projNo)
EDEGREE(empNo, degree)
SUPPLIES (supNo , projNo, partNo , date, quantity)
Topic 3 : Relational Database Design

12. Relational Database Design
Owner#
OwnerName
OwnerAddress
OWNER
Maintenance#
Date
Type
Cost
Perform the complete transformation steps for the E-R Model described in Topic4. 1
(1, N)
own
Building#
Address N
(1, 1)
(1, 1)
incur
Value
(0, N)
MAINTENANCE
PROPERTY 1 N
LeasePeriod
(0, N) 1 N
(0,N)
Bond
for
rent
(1, 1)
Tenant#
FamilyName
FirstName
ContactAddress
Phone#
ACCOUNT N
(1, 1)
ACReceipt#
DateofPayment
TypeOfAccount
AmountPaid N M
(1, N)
pay
TENANT
(1, N) 1 1
Topic 3 : Relational Database Design

13. Relational Database Design
Perform the complete transformation steps for the E-R Model
of the ‘Real Estate Agency’ described in Topic4.
SOLUTION: (to be discussed in the lecture)
Topic 3 : Relational Database Design

14. EER Modeling and transformation
Next Lecture …
Topic 3 (part 2) –
EER Modeling and transformation