Chapter1 - Introduction to Database System

8/17/2019 Chapter1 - Introduction to Database System

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Chapter 1

Introduction to DatabaseSystem


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Traditional File-Based System

A collection of application program thatperform services for the end-users, such asthe production of reports. Each programdenes and manages its o!n data.

"imitation of the #ile $ased System Separation and isolation of data.

Duplication of data.

Data dependence

Incompatible le format.

#i%ed &ueries.

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Database Approach

All the mentioned limitations of the le-based approach can be attributed to t!ofactors(

1. )he denition of the data is embedded inthe application programs, rather than beingstored separately and independently.

'. )here is no control over the access andmanipulation of the data beyond that imposedby the application program.

)o become more e*ective. )he emerging of

database and the D$+S happened.1-


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Database Approach

Analye information needs of anorganiation. Attempt to identify entities,attributes, and relationship. Attribute property that describes some aspect of

the ob0ect that !e !hich to record

elationship association bet!een entities

Entities distinct ob0ect 2person, place, thing,

concept, or event3

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Database ManagementSystem

Database +anagement System A soft!aresystem that enables users to dene, create,maintain, and control access to thedatabase.

A soft!are that interacts !ith the user5sapplication programs and the database.

)ypically, a D$+S provides the follo!ingfacilities.

Allo!s users to dene the database

Allo! user to insert, update, delete and

retrieve data from the database1-6


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Application Program

A computer program that interacts !ith thedatabase by issuing an appropriate re&uestto the D$+S.

7sers interact !ith the database through anumber of application programs that areused to create and maintain the databaseand to generate information.

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Application Program

9ie!s D$+S is an e%tremely po!erful and usefultool !ith this functionality.

D$+S provides another facility :no!n as

vie! mechanism, !hich allo!s each user tohave his or her o!n vie! of the database.

$enets(

9ie!s provide a level of security

9ie!s provide a mechanism to customiethe appearance of the database

9ie! can present a consistent,unchanging picture of the structure of thedatabase.

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Components of the DBMSEnvironment


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Database Design TheParadigm Shift

7ntil no!, !e have ta:en it for granted thatthere is a structure to the data in thedatabase.

#or e%ample, !e have identied four tables.$ut ho! did !e get this structure? )heans!er is &uite simple( the structure of thedatabase is determined during databasedesign.

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!oles in the DatabaseEnvironment

Data and Database Administrator

esponsible for the management of the

data resource, including databaseplanning, development, and maintenanceof standards, policies and procedures andconceptuallogical database.

esponsible for the physical realiation ofthe database, including physical databasedesign and implementation, security,maintenance of the operational system.

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Database Designer

"ogical Database Designer concerned

!ith identifying the data 2the entities,attributes3 the relationship bet!een thedata and the constraints on the data thatis to be stored in the database.

- must have a thorough and completeand complete understanding of theorganiation5s data 2business rules3.

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Database Designer

=hysical database designer decides ho!

the logical database design is to bephysically realied. )his involves(

+apping the logical database designinto a set of tables and integrity

constraintsSelecting specic storage structures

and access methods for the data toachieve good performance.

Designing any security measuresre uired on the data. 1-1


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Application Developers

End-users

Bave users typically una!are of the D$+S Sophisticated users user !hich is familiar !ith

the structure of the database and the facilitieso*ered by the D$+S.

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Database Environment

+a0or aim of a database system is to provide users!ith an abstract vie! of data, hiding certain details ofdata is stored and manipulated.

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)he )hree-"evel ABSI-S=ACArchitecture

E%ternal "evel )he 7sers vie! of the database. )hislevel describes that part of the database that isrelevant to each other.

Conceptual "evel )he community vie! of thedatabase. )his level describes !hat data is stored inthe database and the relationship among the data.

Internal "evel the physical representation of thedata on the computer. )his level describes ho! the

data is stored in the database.

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Data +odels and Conceptual+odeling

Data +odel an integrated collection of conceptsfor describing and manipulating data, relationshipbet!een data and constraints on the data in an

organiation.+odel representation of real-!orld ob0ects and

events and their association.

Data model represent the organiation itself.

=rovide the basic concepts and notations that!ill allo! database designers and end-user tocommunicate unambiguously and accuratelytheir understanding of the organiational data.

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Data +odels and Conceptual+odeling

Data model can be thought of as comprising threecomponents( A structural part, consisting of a set of rules according to

!hich databases can be constructed. A manipulated part, dening the types of operation that

are allo!ed on the data 2this includes the operations thatare used for updating or retrieving data from the databaseand for changing the structured of the database3.

A set of integrity constraints, !hich ensures that the datais accurate.

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Chapter1 - Introduction to Database System