Part A

Aim: Understanding of Entity-Relationship (ER) diagram and draw ER Model for a given
database.

Prerequisite: Software Engineering

Outcome: ER Diagram for a given database scenario.
Theory:
The ER data model was developed to facilitate the database design by allowing
specification of an enterprise schema that represents the overall logical structure
of the database. The ER model data model is one of the several data models. The
semantic aspect of the model lies in its representation of the meaning of the data.
The ER model is very useful many database design tools drawn on concepts from
the ER model. The ER model employs 3 basic notations: entity set, relationship
set and attributes.
Symbols Used in ER Notation
Entity set: An entity is a set of
Entity entities of the same type that
share the properties or
attributes.
Weak entity set: An entity set
may not have sufficient
Entity
attributes to form a primary
key. Such an entity set is
termed as weak entity set.
Relationship Set: A
relationship is an association
R
among several entities. A
relationship set is a set of
relationship of the same type.
Identification relationship
set for weak entity set : The
R relationship associating the
weak entity set with the
identifying entity set is called
the identifying relationship.
Primary key : The primary
key is used to denote a
A candidate key that is chosen by
the database designers as the
principal means of identifying
entities within an entity set.
Attribute
A

Multi valued Attribute

A
 Derived Attribute
A

Many to many relationship

R

1 1 One to one relationship

R

1 N One to many relationship

R

Total Participation of entity

R Entity set in relationship: The
participation of an entity set E
in a relationship set R is said to
be total if every entity in E
participates in at least one
relationship in R.
Exercise:
List the data requirements for the database of the company which keeps track of the
company employee, department and projects. The
database designers provide the following description
1. The company is organized into departments. Each department has unique name,
unique number, and particular employee to manage the department. We keep
track of the start date and the employee begins managing the department. The
department has several locations.
2. The department controls a number of projects each of which has a unique name,
unique number and a single location.
3. We store each employee names social security number, address, salary, sex and
dob. An employee is assigned one department but may work on several projects
which are not necessarily controlled by the same department. We keep track of
the department of each employee works on each project and for insurance
purpose. We keep each dependents first name, sex, dob and relation.
Instructions:
1. Students should complete the part B of the manual and shall upload this
assignment on web portal with the file name “SCPA2_Rollnumber.doc”
 Part B
ER Diagram:
PASTE the ER diagram here.
Observation & Learning:
Write your Observations & Learning after performing task
Conclusion:
Write statement of conclusion here