COM 322:
Introduction to Database
Systems
Course Lecturer:
Richard Ngwira
Nalikule College of Education- COM 322: Introduction to
Database Systems
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Outline of the course
1.
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3.
4.
5.
6.
7.
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Introduction to databases
Database System Architecture
Relational Data Modelling using ERD
Normalization
Relational Algebra and Relational Calculus
SQL: Data Manipulation
SQL: Data Definition
Database Administration
Nalikule College of Education- COM 322: Introduction to
Database Systems
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Modes of Assessment
1. Continuous Assessment: 40% Distributed as follows
• Assignments + Lab work
10%
• Quizes/Tests
10%
• Mid Semester Examinations 20%
2. End of Semester examinations
60%
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Database Systems
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Topic 1.
Introduction to Databases
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Database Systems
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Lecture Outline
• Introduction
• Traditional File-Based Systems
• Database Approach
• Roles in Database Environment
• History of Database
• Advantages and Disadvantages of DBMS
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Database Systems
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Introduction
• The database is now such an integral part of our day-to-day life that often
we are not aware we are using one.
• The information technology has changed rapidly, many computing
applications deal with large amounts of information regularly.
• As the end user applications has changed significantly in last few decades,
there is a challenge to store the large amount of information, retrieve and
manage this information in timely manner.
• This can be achieving today by making use of services of
Database Management System (DBMS).
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Introduction
Cont’d
• Today DBMS not only used to insert, update and delete the data
stored in database.
• The job of DBMS system is to collect the data, give a systematic
representation to it and also provides ways for the data to be modified or
extracted by users or other programs.
• As the technology has grown rapidly in past four decades, today DBMS has
gain its own importance because the data has brought online in the hands
of end user through different computer networking.
• Our world is driven with lot of exciting applications such as multimedia
databases, live streaming of data, digital had made our life much easier to
deal with data.
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Database Systems
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Database Applications
The growth of DBMS system has not only benefitted only to the customers or
employees in an organization but it has touched all the aspects of our lives. Some
of the areas where database is applied are:
Transportation: DBMS system can be used for reservation or cancellation of
tickets and can be also used to check for the schedules of incoming and outgoing
flights.
Education: DBMS system can be used by different universities to allow students
take admission online, checking the status of vacant seats, enrolment system can
be done computerized etc.
Banking: DBMS system have completely changed the face of the banking sector.
Few decades ago, the banking system was purely the paper based system have
now transformed in keeping less of paper work.
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Database Systems
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Database Applications
Sales: DBMS system allows the data to be stored in electronic format by making
use of relational databases which allows the data to be stored in highly organised
manner. This database allows the information such as information about the
customers, products, sales, purchases etc to be stored in database.
Manufacturing: DBMS system allows the user to store information about the
production of goods, the inventory details, the total number of orders, supply
chain information in database so that it allows the decision makers to make
critical decisions in timely manner.
Human Resource: DBMS has made the life of HR team much better by allowing
the team to compute tax deductions, employee wages, retrieving the details of
the employees in faster manner as compared to traditional paper based approach
which was time consuming.
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Database Systems
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Traditional File-Based System
• It is a collection of application programs that perform services for the endusers such as the production of reports. Each program defines
and manages its own data.
• A file is simply a collection of records, which contains logically related
data. Each record contains a logically connected set of one or more fields,
where each field represents some characteristic of the real-world object
that is being modeled.
• A time when there were no database system, file system was the only way
to store, retrieve and manage data.
• Consider the scenario of a University administration using file oriented
system.
Nalikule College of Education- COM 322: Introduction to
Database Systems
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Traditional File-Based System
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Database Systems
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Traditional File-Based System
Assumptions:
• A file named “General Data” may contain name, registration no,
address and other information of the student.
• The file “Grade Data” includes the results of oral exam, written
exams, seminars, projects etc.
• Class Data additionally comprises the attendances of the students.
• While generating the student’s progress report, the three files must
be updated to give the consistent report.
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Database Systems
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An example of a File
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Database Systems
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Limitations of the File-Based Approach
1. Data Redundancy:
• It is possible that the same information may be duplicated in different files. This leads to data
redundancy results in memory wastage.
2. Data Inconsistency:
• Because of data redundancy, it is possible that data may not be in consistent state.
3. Difficulty in Accessing Data:
• Accessing data is not convenient and efficient in file processing system.
4. Limited Data Sharing:
• Data are scattered in various files. Also different files may have different formats and these files
may be stored in different folders may be of different departments. So, due to this data isolation,
it is difficult to share data among different applications.
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Limitations of the File-Based Approach
5.
Integrity Problems:
• Data integrity means that the data contained in the database is both correct and consistent.
For this purpose the data stored in database must satisfy correct and constraints.
6. Atomicity Problems:
• Any operation on database must be atomic. This means, it must happen in it do entirely or
not at all.
7. Concurrent Access Anomalies:
• A file-based system must manage, or prevent, concurrency by the application programs.
Typically, in a file-based system, when an application opens a file, that file is locked.
• This means that no one else has access to the file at the same time.
8. Security Problems:
• Database should be accessible to users in limited way. Each user should be allowed to access
data concerning his requirements only.
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The Database
• All the above limitations of the file-based approach can be attributed to
two factors:
1. the definition of the data is embedded in the application programs, rather than
being stored separately and independently;
2.
there is no control over the access and manipulation of data beyond that imposed
by the application programs.
To become more effective, a new approach was required.
What emerged were the database and the Database Management System (DBMS).
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The Database
• It is a shared collection of logically related data, and a description of this data,
designed to meet the information needs of an organization.
• Instead of disconnected files with redundant data, all data items are
integrated with a minimum amount of duplication.
• The database is no longer owned by one department but is a shared corporate
resource.
• The database holds not only the organization’s operational data but also a
description of this data.
• It is also defined as a self-describing collection of integrated records.
• The description of the data is known as the system catalog (or data dictionary or
metadata – the ‘data about data’).
• It is the self-describing nature of a database that provides program–data
independence.
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The Database System and Database
management System (DBMS)
• Database system is a system to achieve an organized, store a large number of
dynamical associated data, facilitate for multi-user accessing to computer
hardware, software and data, that it is a computer system with database
technology.
• A database system aims to achieve a highly organized collection of data along
with appropriate tools and applications that facilitate processing and access to
that data.
• A DBMS is a software system that enables users to define, create, maintain, and
control access to the database.
• The DBMS is the software that interacts with the users’ application programs and
the database.
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Database Systems
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The Database System and Database
management System (DBMS)
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Database Systems
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Characteristics of Database Management
System (DBMS)
A modern DBMS has the following characteristics:
• Real-world entity: A modern DBMS is more realistic and uses real-world entities
to design its architecture. It uses the behavior and attributes too. For example, a
school database may use students as an entity and their age as an attribute.
• Relation-based tables: DBMS allows entities and relations among them to form
tables. A user can understand the architecture of a database just by looking at the
table names.
• Isolation of data and application: A database system is entirely different than its
data. A database is an active entity, whereas data is said to be passive, on which
the database works and organizes. DBMS also stores metadata, which is data
about data, to ease its own process.
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Database Systems
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Characteristics of Database Management
System (DBMS)
• Less redundancy: DBMS follows the rules of normalization, which splits a relation
when any of its attributes is having redundancy in values. Normalization is a
mathematically rich and scientific process that reduces data redundancy.
• Consistency: Consistency is a state where every relation in a database remains
consistent. There exist methods and techniques, which can detect attempt of
leaving database in inconsistent state. A DBMS can provide greater consistency as
compared to earlier forms of data storing applications like file-processing
systems.
• Query Language: DBMS is equipped with query language, which makes it more
efficient to retrieve and manipulate data. A user can apply as many and as
different filtering options as required to retrieve a set of data.
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Database Systems
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Characteristics of Database Management
System (DBMS)
• ACID Properties: DBMS follows the concepts of Atomicity, Consistency, Isolation,
and Durability (normally shortened as ACID). These concepts are applied on
transactions, which manipulate data in a database. ACID properties help the
database stay healthy in multi-transactional environments and in case of failure.
• Multiuser and Concurrent Access: DBMS supports multi-user environment and
allows them to access and manipulate data in parallel. Though there are
restrictions on transactions when users attempt to handle the same data item,
but users are always unaware of them.
• Multiple views: DBMS offers multiple views for different users. A user who is in
the Sales department will have a different view of database than a person
working in the Production department. This feature enables the users to have a
concentrate view of the database according to their requirements.
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Components of the DBMS Environment
• There are five major components in the DBMS environment:
hardware, software, data, procedures, and people.
Components of DBMS environment
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Components of the DBMS Environment
• Hardware
The DBMS and the applications require hardware to run.
• The hardware can range from a single personal computer, to a single
mainframe, to a network of computers.
• The particular hardware depends on the organization’s requirements and
the DBMS used. Some DBMSs run only on particular hardware or operating
systems, while others run on a wide variety of hardware and operating
systems.
• A DBMS requires a minimum amount of main memory and disk space to
run, but this minimum configuration may not necessarily give acceptable
performance.
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Components of the DBMS Environment
• Software
The software component comprises the DBMS software itself and the application
programs, together with the operating system, including network software if the DBMS is
being used over a network.
• Data
The most important component of the DBMS environment, certainly from the end-users’
point of view, is the data.
• Procedures
Procedures refer to the instructions and rules that govern the design and use of the
database. The users of the system and the staff that manage the database require
documented procedures on how to use or run the system.
• People
The final component is the people involved with the system.
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Roles in the Database Environment
The following types of people are the key participants in the DBMS
environment;
• data and database administrators
• Database designers
• application developers and
• the end-users.
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Data and Database Administrators
• The Data Administrator (DA) is responsible for the management of the data
resource including database planning, development and maintenance of
standards, policies and procedures, and conceptual/logical database
design.
• The DA consults with and advises senior managers, ensuring that the
direction of database development will ultimately support corporate
objectives.
• The Database Administrator (DBA) is responsible for the physical
realization of the database, including physical database design and
implementation, security and integrity control, maintenance of the
operational system, and ensuring satisfactory performance of the
applications for users.
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Database Designers
a. Logical Database Designer
• is concerned with identifying the data (that is, the entities and attributes),
the relationships between the data, and the constraints on the data that is
to be stored in the database.
• The logical database designer must have a thorough and complete
understanding of the organization’s data and any constraints on this data
(the constraints are sometimes called business rules).
• These constraints describe the main characteristics of the data as viewed
by the organization.
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Database Designers
b. Physical Database Designer
Decides how the logical database design is to be physically realized. This
involves:
• mapping the logical database design into a set of tables and integrity
constraints;
• selecting specific storage structures and access methods for the data to
achieve good performance;
• designing any security measures required on the data.
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Application Developers
• These are computer professionals who write application programs,
used to develop user interfaces.
• The application programmer uses Rapid Application Development
(RAD) toolkit or special type of programming languages which include
special features to facilitate generation of forms and display of date
on screen.
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End-Users
1. Naive users:
These are the unsophisticated users who interact with the system by
invoking one of the application programs that have been written
previously.
E.g. consider a user who checks for account balance information over
the World Wide Web. Such a user access a form, enters the account
number and password etc.
And the application program on the internet then retrieves the account
balance using given account information which s passed to the user.
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End-Users
2. Sophisticated users:
These users interact with the database using database query language.
They submit their query to the query processor.
Then Data Manipulation Language (DML) functions are performed on
the database to retrieve the data. Tools used by these users are OLAP
(Online Analytical Processing) and data mining tools.
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Reading Assignment
• Discuss the History of Database Management Systems.
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Advantages of DBMSs
1. Improved data sharing:
The DBMS helps create an environment in which end users have better access to
more and better-managed data.
Such access makes it possible for end users to respond quickly to changes in their
environment.
2. Improved data security:
The more users access the data, the greater the risks of data security breaches.
Corporations invest considerable amounts of time, effort, and money to ensure that
corporate data are used properly.
A DBMS provides a framework for better enforcement of data privacy and security
policies.
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Advantages of DBMS
. Better data integration:
3
Wider access to well-managed data promotes an integrated view of
the organization’s operations and a clearer view of the big picture.
 It becomes much easier to see how actions in one segment of the company
affect other segments.
4. Minimized data inconsistency:
Data inconsistency exists when different versions of the same data appear in
different places.
The probability of data inconsistency is greatly reduced in a properly designed
database.
5. Improved data access:
 The DBMS makes it possible to produce quick answers to ad hoc queries.
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Advantages of DBMS
6. Improved decision making:
 Better-managed data and improved data access make it possible to generate
better-quality information, on which better decisions are based.
The quality of the information generated depends on the quality of the
underlying data.
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Disadvantages of DBMS
1. Increased costs:
Database systems require sophisticated hardware and software and highly
skilled personnel.
The cost of maintaining the hardware, software, and personnel required to
operate and manage a database system can be substantial.
Training, licensing, and regulation compliance costs are often overlooked
when database systems are implemented.
2. Management complexity:
Database systems interface with many different technologies and
have a significant impact on a company’s resources and culture.
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Disadvantages of DBMS
3. Maintaining currency:
To maximize the efficiency of the database system, you must keep your system
current.
Therefore, you must perform frequent updates and apply the latest patches and
security measures to all components.
4. Frequent upgrade/replacement cycles:
DBMS vendors frequently upgrade their products by adding new functionality. Such
new features often come bundled in new upgrade versions of the software.
Some of these versions require hardware upgrades. Not only do the upgrades
themselves cost money, but it also costs money to train database users and
administrators to properly use and manage the new features.
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Database Systems
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End of Lesson 1
Thank you!
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Database Systems
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