1. Conceptual Data Modeling Using Entities & Relationships

2. High Level Conceptual Data Models
Conceptual Design is a important phase in designing successful database applications
Entity Relationship Model is the popular high level conceptual data model
Object Modelling is also gaining the importance – Unified Modelling Language

3. A Sample Database Application
Considering Company as a Mini world Problem we need to design the Database.
Company Database consists of:
Company Info
Employee Info
Project Info
The Formulated Requirements are:
The company is organized into departments. Each department has a unique name, a unique number, and a particular employee who manages the department. We keep track of the start date when that employee began managing the department. A department may have several location
A department controls a number of projects, each of which has a unique name, a unique number, and a single location
We store each employee’s name, Social Security number, address, salary, sex (gender), and birth date. An employee is assigned to one department, but may work on several projects, which are not necessarily controlled by the same department. We keep track of the current number of hours per week that an employee works on each project. We also keep track of the direct supervisor of each employee (who is another employee).
We want to keep track of the dependents of each employee for insurance purposes

4. A Sample Database Application

5. Entity Types, Entity Sets, Attributes & Keys
Entities and Attributes
The basic object that the ER model represents is an Entity – Physical or Conceptual Existence
Each Entity has Attributes – Particular Properties
Types of Attributes
Simple Vs Composite
Single Vs Multi valued
Stored Vs Derived
NULL Values
Composite Attributes

6. Entity Types, Entity Sets, Attributes & Keys
Entity Types, Entity Sets, Keys, and Value Sets
An entity type defines a collection (or set) of entities that have the same attributes
The collection of all entities of a particular entity type in the database at any point in time is called an entity set
Key Attributes of an Entity Type
Uniqueness constraint - key attribute
Weak Entity
Value Sets of Attribute
Mathematically, an attribute A of entity set E whose
value set is V can be defined as a function from E to
the power set P(V) of V -- A : E → P(V)
[Entity Set]
Employee
(Name, Age, Salary..)
E1 – [John Smith, 55, 80k]
E2 – [Fred Brown, 50, 60k]
[Entity Set]
Department
(Name, Location, Manager..)
D1 – [Finance, Delhi, John Smith]
D2 – [Sales, Hubballi, Fred Brown]

7. Conceptual Design of COMPANY Database
Department, Project, Employee and Dependents – Entity Types

8. Relationship Types, Relationship Sets, Roles and Structural Constraints
Relationship Types, Sets, and Instances
A relationship type R among n entity types E1, E2, ..., En defines a set of associations —or a relationship set
Mathematically, the relationship set R is a set of relationship instances ri, where each ri associates n individual entities (e1,e2,...,en)
Relationship Degree, Role Names, and Recursive Relationships
Degree of a Relationship Type
Binary and Ternary Degree
The degree of a relationship type is the number of
participating entity type

9. Relationship Types, Relationship Sets, Roles and Structural Constraints
Relationship as Attribute
Role Names and Recursive Relationships
Cardinality Ratios for Binary Relationships
Participation Constraints and Existence Dependencies

10. Weak Entity Types
The Entity Type that doesn’t have any key attribute - Weak Entity
Strong Entity Type & Identifying Relationship
A weak entity type normally has a partial key
Redefining the ER Diagram – Company Database
MANAGES, a 1:1 relationship type between EMPLOYEE and DEPARTMENT
WORKS_FOR, a 1:N relationship type between DEPARTMENT and EMPLOYEE. Both participations are total
CONTROLS, a 1:N relationship type between DEPARTMENT and PROJECT
SUPERVISION, a 1:N relationship type between EMPLOYEE
WORKS_ON, determined to be an M:N relationship type with attribute Hours
DEPENDENTS_OF, a 1:N relationship type between EMPLOYEE and DEPENDENT

11. ER Diagram

12. Thank You!!!