Chapter 1 - Introduction to Database Systems.ppt

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1. 7/2/20241
Fundamentals of Database System
Dilla University
College of Engineering and Technology
Department of Computer Science

2. Introduction
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Data: What is data?
Facts concerning people, objects, events or other entities.
Can be in the form of text, graphics, sound and video segments
They are difficult to interpret or make decisions based on
Unprocessed, raw facts and can be stored in database
Information: What is Information?
Data presented in a form suitable for interpretation.
Data processed to be useful in decision making.
Processed data
Can’t be stored in database

3. Introduction … cont’d
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Database: What is database?
An organized collection of logicallyrelated data.
A shared collectionof logically interrelated data designed to
meet the varied information needs of an organization.
A shared collection –can be used simultaneously by many
department and user
Logically related -comprise the important objects and the
relationships between these objects
A computerized means of record keeping system

4. Introduction …. cont’d
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A database has the following implicit properties:
A database represents some aspect of the real world,
sometimes called the mini world or the Universe of Discourse
(UoD).
Changes to the mini world are reflected in the database.
A database is a logically coherent collection of data with some
inherent meaning.
A random assortment of data cannot correctly be referred to as a
database.
A database is designed, built, and populated with data for a
specific purpose.

5. Introduction …. cont’d
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Course SectionSemester Name Rank
MIS 3353 100 Su 01 Kemp Instr
MIS 3353 200 Su 01 Schwarzkopf Assoc P
MIS 3373 200 Su 01 Kemp Instr
MIS 4663 900 Fa 01 Schwarzkopf Assoc P
MIS 4663 901 Fa01 Van Horn Prof
Data

6. Introduction … cont’d
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Meta Data: What do we mean by meta data?
Descriptions of the properties or characteristics of the data,
including data types, field sizes, allowable values, and
documentation
Data that describes data
Data about data
Description of fields
Display and format instructions
Structure of files and tables
Security and access rules
Triggers and operational rules

7. Introduction …. cont’d
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Metadata
Data Item Value
Name Type Length Min Max Description
Course Char 7 Three digit depart-
ment reference and
4 digit
Section Integer 3 001 900 Section number
Semester Char 10 Semester and year
Name Char 30 Instructor name
Rank Char 10 Instructor rank

8. Data management approaches
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Data management : keeping your data records
We have three approaches
Manual Approach
File-Based Approach
Database Approach
Manual File Handling Systems
The primitive and traditional way of information handling
This may work well if the number of items to be stored is small.
Includes intensive human labor
Events and objects are written on files (paper)
Each of the files containing various kinds of information is labeled and
stored in one or more cabinets
The cabinets could be kept in safe places for security

9. Manual File Handling Systems ..cont’d
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Limitations of Manual File Handling
Problem of Data Organization
Problem of Efficiency
Prone to error
Difficult to update, retrieve, integrate
You have the data but it is difficult to compile the information
Significant amount of duplication of data
Cross referencing is difficult
Two computerized approaches evolved to overcome the
limitations of the above approaches
 File based approach decentralised
 Database approachcentralised

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File based systems were an early attempt to computerize the manual
filing system.
It is a decentralized computerized data handling method i.e. to
develop a program or a number of programs for each different
application.
Since every application defines and manages its own data, the system
is subjected to serious data duplication problem.
File basedApproach

11. Limitations of File-Based systems
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Data Redundancy (Duplication of data)
Same data is held by different programs
Staffsalary(staffno, name, sex, salary)
Staff(staffno,name,position,sex,dateofb,salary)
Wasted space (Uncontrolled duplication of data)
Separation and isolation of data
–Each program maintains its own set of data. Users of one program
may be unaware of potentially useful data held by other programs.
Limited data sharing-No centralized control of data
Data Inconsistency and confusion
Data dependence
File structure is defined in the program code and is dependent on
the application programming language.

12. Limitations of File-Based systems .. Cont’d
Incompatible file formats -Lack of data sharing and availability)
Programs are written in different languages, and so cannot easily
access each others files.
E.g. Personnel write in C, Payroll writes in COBOL
Poor Security and administration
Update Anomalies
Modification Anomalies
Deletion Anomalies
Insertion Anomalies
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13. Database Approach
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Here, a single repository of data is maintained.
What emerged were the database and database management systems
Basic Database terminologies
Enterprise: an organization like library, bank, university, etc.
Entity: Person, place, thing, or event about which we wish to keep
data
Attribute (Field): Property of an entity. E.g. Name, age,
telephone, grade, sex, etc.
Record: A logically connected set of one or more Attributes that
describe a person, place or thing. (Logically related data)
File: A collection of related records. E.g. Student file
Relationship: an association among entities (entity records)
Query: question asked for database

14. Benefits of Database systems
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Data can be shared: two or more users can access and use.
Improved data accessibility: By using structured query languages,
the users can easily access data without programming experience.
Redundancy can be reduced: Isolated data is integrated in
database.
Quality data can be maintained: the different integrity constraints
in the database approach will maintain the quality leading to better
decision making.
Inconsistency can be avoided: controlled data redundancy will
avoid inconsistency of the data in the database to some extent.
Transaction support can be provided: basic demands of any
transaction support systems are implanted in a full scale DBMS.

15. Benefits of Database systems … cont’d
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Integrity can be maintained: Data at different applications will be
integrated together with additional constraints.
Security measures can be enforced: The shared data can be secured
by data security mechanisms.
Improved decision support: the database will provide information
useful for decision making
Standards can be enforced: ways of using different data by users
Less Labor: data maintenance will not demand much resource
Centralized information control: Since relevant data in the
organization will be stored at one repository, it can be controlled and
managed at the central level.
Data Independence -Applications insulated from how data is
structured and stored

16. Limitations and risk of database approach
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Introduction of new professional and specialized personnel
High cost to be incurred to develop and maintain the system
Complex backup and recovery services from the users
perspective
High impact on the system when failure occurs to the central
system

17. Users and Actors of Database System
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Actorsonthescene:Thepeoplewhosejobsinvolvetheday-to-day
useofalargedatabase
Workersbehindthescene:Thosewhoworktomaintainthe
databasesystemenvironment,butwhoarenotactivelyinterestedin
thedatabaseitself.
Actors on the Scene
Database Administrators
Database Designers
End Users
System Analysts and Application Programmers (Software Engineers)

18. Database Administrators
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In a database environment, the primary resource is the database itself
and the secondary resource is the DBMS and related software.
Administering these resources is the responsibility of the Database
Administrator (DBA).
The DBA is responsible for authorizing access to the database, for
coordinating and monitoring its use, and for acquiring software and
hardware resources as needed.
The DBA is accountable for problems such as breach of security or
poor system response time.

19. Database Designer
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Database designersare responsible for identifying the data to be stored
in the database and for choosing appropriate structures to represent and
store this data.
It is the responsibility of database designers to communicate with all
prospective database users, in order to understand their requirements,
and to come up with a design that meets these requirements.
In many cases, the designers are on the staff of the DBAand may be
assigned other staff responsibilities after the database design is
completed.
The final database design must be capable of supporting the
requirements of all user groups.

20. End Users
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End users are the people whose jobs require access to the database for
querying, updating, and generating reports;
The database primarily exists for their use. There are several categories
of end users:
Casual end users:-occasionally access the database. They are
typically middle or high-level managers or other occasional
browsers.
Naive orparametric end users:-Their main job revolves around
constantly querying and updating the database, using standard types
of queries and updates called cannedtransactionsthat have been
carefully programmed and tested.
Bank tellers check account balances and post withdrawals and deposits
Reservation clerks for airlines, hotels, and car rental companies check
availability for a given request and make reservations

21. End Users … Cont’d
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Sophisticated end users: Include engineers, scientists, business
analysts, and others who thoroughly familiarize themselves with
the facilities of the DBMS so as to implement their applications to
meet their complex requirements.
Stand-alone users:Maintain personal databases by using ready
made program packages that provide easy to use menu or graphics
based interfaces.
An example is the user of a tax package that stores a variety of
personal financial data for tax purposes.

22. System Analysts and Application
Programmers (Software Engineers )
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System analysts: Determine the requirements of end users, especially
naive and parametric end users, and develop specifications for canned
transactions that meet these requirements.
Application programmers implement these specifications as programs;
then they test, debug, document, and maintain these canned
transactions.
Such analysts and programmers (nowadays called software engineers)
should be familiar with the full range of capabilities provided by the
DBMSto accomplish their tasks.

23. Workers behind the Scene
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These persons are typically not interested in the database itself.
These include:
DBMS system designers and implementers:-are persons who
design and implement the DBMS modules and interfaces as a
software package.
A DBMS is a complex software system that consists of many
components or modules, including modules for implementing the
catalog, query language, interface processors, data access,
concurrency control, recovery, and security.
The DBMS must interface with other system software, such as the
operating system and compilers for various programming
languages

24. Workers behind the Scene … cont’d
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Tooldevelopers:Includepersonswhodesignandimplementtools
Toolsaresoftwarepackagesthatfacilitatedatabasesystemdesignand
use,andhelpimproveperformance.
Toolsareoptionalpackagesthatareoftenpurchasedseparately.
Theyincludepackagesfordatabasedesign,performancemonitoring,
naturallanguageorgraphicalinterfaces,prototyping,simulation,and
testdatageneration.
Operatorsandmaintenancepersonnel:arethesystem
administrationpersonnelwhoareresponsiblefortheactualrunning
andmaintenanceofthehardwareandsoftwareenvironmentforthe
databasesystem.

25. Some Common uses of Databases
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In a university
Containing information about a student, the course she/he is enrolled
in, the dormitory she/he has been given.
Containing details of Staff who work at the university at personnel,
payroll, etc.
In a library
There may be a database containing details of the books in the library
and details of the users,
The database system handles activities such as
Allowing a user to reserve a book
Notifying when materials are overdue:

26. Some Common uses of Databases … Cont’d
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In travel agencies
When you make inquiries about a travel, the travel agent may access
databases containing flight details
Flight no., date, time of departure, time of arrival
Insurance
When you wish to take out insurance, there is database containing
Your personal details: name, address, age
information on whether you drink or smoke,
Your medical records to determine the cost of the insurance
Supermarkets
When you buy goods from some supermarkets, a database will be accessed.
The checkout assistant will run a barcode reader over the purchases.

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