This document outlines the key concepts of database systems and the entity-relationship model. It defines what a database is, the advantages of using database management systems, and common DBMS architectures. It also explains the core components of the entity-relationship model including entities, attributes, relationships, keys, and degrees of relationships. The document provides examples and definitions to illustrate database and ER model concepts.

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Dr. Ramadan Babers
Faculty of Science - Helwan University
Fall-2018
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Introduction
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3. Unit01 Outlines
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4. Unit01 Outlines
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5. Unit01 Outlines
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6. Unit01 Outlines
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7. Unit01 Outlines
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8. Unit01 Outlines
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9. Unit01 Outlines
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10. + Database Systems
Basic Concepts
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11. Unit01 Outlines
 Types of Databases and Database Applications
 Basic Definitions
 Typical DBMS Functionality
 Examples of a Database
 Main Characteristics of the Database Approach
 Database Users
 Advantages of Using the Database Approach
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12. Introduction
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13. Introduction
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14. Examples of Database Applications
• Purchases from the supermarket
• Purchases using your credit card
• Booking a holiday at the travel agents
• Using the local library
• Taking out insurance
• Studying at university
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15. File-Based Systems
 Collection of application programs that perform
services for the end users (e.g. reports).
 Each program defines and manages its own data.
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16. File-Based Processing
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17. Database Systems
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18. Definitions
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 Data: known facts that can be recorded
 Database: a collection of data
 represents some aspect of the real world
 logically coherent collection (not a random collection)
 designed, built & populated for a specific purpose
 Database Management System: the software
that manages the data

19. Database Management System (DBMS)
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20. Advantages of DBMSs
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 Control of data redundancy
 Data consistency
 More information from the same amount of data
 Sharing of data
 Improved data integrity
 Improved security
 Enforcement of standards

21. Advantages of DBMSs
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 Improved data accessibility and responsiveness
 Increased productivity
 Improved maintenance through data
independence
 Increased concurrency
 Improved backup and recovery services

22. Disadvantages of DBMSs
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 Complexity
 Size
 Cost of DBMS
 Additional hardware costs
 Cost of conversion
 Higher impact of a failure

23. Database Activity Conceptual Data Modeling
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Project Identification
and Selection
Project Initiation
and Planning
Analysis
Physical Design
Implementation
Maintenance
Logical Design

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DBMS Architecture
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25. Architecture
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 DBMS can be seen as either single tier or multi-tier.
Database (Data) Tier: At this tier,
the database resides along with its query
processing languages. Relations, data and
their constraints exist at this level.
Application (Middle) Tier: sits in
the middle and acts as a mediator
between the end-user and the database.
User (Presentation) Tier: multiple
views of the database can be provided by
the application.All views are generated by
applications that reside in the application
tier.

26. Data Models
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 Data models
 Define how the logical structure of a database is modeled.
 Are fundamental entities to introduce abstraction in a
DBMS.
 Define how data is connected to each other
(Relationships) and how they are processed and stored
inside the system.
The first data model could be flat data-models, where all the
data used are to be kept in the same plane and contain lots of
duplication and update anomalies.

27. Entity-Relationship Model (ER Model)
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 ER Model contains:
1) Entity set,
2) Relationship set,
3) General attributes, and
4) Constraints.
Entity
Attributes

28. Entity-Relationship Model (ER Model)
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1) Entity
 An entity can be a real-world object. For
example, in a school database, students,
teachers, classes, and courses offered can
be considered as entities.
 All these entities have some attributes or
properties that give them their identity.
 An entity set is a collection of similar
types of entities.

29. Entity-Relationship Model (ER Model)
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2) Attribute
 Entities are represented by means of their
properties called attributes. All attributes have
values. For example, a student entity may have
name, class, and age as attributes.

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 There exists a domain or range of values that can
be assigned to attributes. For example, a student's
name cannot be a numeric value. It has to be
alphabetic. A student's age cannot be negative, etc.

31. Entity-Relationship Model (ER Model)
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Types of Attributes
Simple attributes:
are atomic values. For example, a
student's phone number is an
atomic value of 10 digits.
Composite attribute:
are made of more than one
simple attribute. For example, a
student's complete name may
have first_name and last_name.

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Types of Attributes
Multivalued: attributes
are depicted by double ellipse.
Derived attribute:
are the attributes that do not
exist in the physical database,
but their values are derived
from other attributes present
in the database. For example,
average_salary and age.

33. Entity-Relationship Model (ER Model)
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Entity-Set and Keys
Key is an attribute or collection of attributes that uniquely
identifies an entity among entity set.
For example, the ID_number of a student makes him/her
identifiable among students.
Keys Types
 Super Key: A set of attributes (one or more) that collectively
identifies an entity in an entity set.
 Candidate Key: A minimal super key is called a candidate key.
An entity set may have more than one candidate key.
 Primary Key: A primary key is one of the candidate keys
chosen by the database designer to uniquely identify the entity set.

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3) Relationship
 The relationship is the association among entities.
For example, an employee works_at a
department, a student enrolls in a course. Here,
Works_at and Enrolls are called relationships.
Employee Departmrnt
Student Course
Works at
enrolls

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Degree of Relationship
The number of participating entities in a relationship
defines the degree of the relationship.

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Degree of Relationship
One-to-one: One entity from entity set A can be
associated with at most one entity of entity set B and
vice versa.

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Degree of Relationship
One-to-many: One entity from entity set A can be
associated with more than one entities of entity set
B, however an entity from entity set B can be
associated with at most one entity.

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Degree of Relationship
Many-to-many: One entity from A can be associated
with more than one entity from B and vice versa.