1. Relational Database Design (Top Down)
CSE2DBF – CSE4DBF
Relational Database Design (Top Down)
07/03/2017
Reading: Elmasri and Navathe, “Fundamentals of Database Systems, Chapter 9”, Pearson, 2017.

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 in Topic 4.

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

4. 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 regular 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)

5. 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 key of the weak entity itself.
Employee
empNo
name
address
degree
1 (0, m)
has
M (1, 1)
Dependent
dependentName
dateOfBirth
DEPENDENT
(empNo, dependentName, dateOfBirth)

6. 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 other relation.
Department
deptNo
deptName
manages
Employee
empNo
name
address
degree
1 (0, 1)
1 (1, 1)
DEPARTMENT( deptNo, deptName, mngrEmpNo)

7. Transformation of E-R Model into Relational Logical Model (Top Down design)
STEP 4: 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).
Department
deptNo
deptName
Employee
empNo
name
address
degree
M (1, 1)
1 (1, m)
works for
EMPLOYEE (empNo, name, address, deptNo)

8. 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
empNo
name
address
degree
M (1, m)
works on
projNo
M (1, m)
projName
Project
WORKS ON (empNo, projNo)

9. 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, deptNo)
EDEGREE(empNo, degree)

10. 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.
supplies
quantity
date
M (1, m)
M (0, m)
Project
projNo
projName
Supplier
supNo
supName
Part
partNo
partName
SUPPLIES (supNo , projNo, partNo , date, quantity)

11. Transformation of E-R Model into Relational Logical Model (Top Down 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)

12. Relational Database Design
Perform the complete transformation steps for the E-R Model
of the ‘Real Estate Agency’ described in Topic 2.
SOLUTION: (to be discussed in the lecture)

13. EER Modelling and Transformation
Next Lecture
EER Modelling and Transformation
Reading:
Elmasri and Navathe, “Fundamentals of Database Systems, Chapters 4 & 9”, Pearson, 2017

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