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Chapter 1Chapter 1

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Chapter 1 - ObjectivesChapter 1 - Objectives

Some common uses of database systems.Some common uses of database systems. Characteristics of file-based systems.Characteristics of file-based systems. Problems with file-based approach.Problems with file-based approach. Meaning of the term database.Meaning of the term database. Meaning of the term Database Meaning of the term Database

Management System (DBMS).Management System (DBMS).

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Chapter 1 - Objectives Chapter 1 - Objectives

Typical functions of a DBMS.Typical functions of a DBMS. Major components of the DBMS Major components of the DBMS

environment.environment. Personnel involved in the DBMS Personnel involved in the DBMS

environment.environment. History of the development of DBMSs.History of the development of DBMSs. Advantages and disadvantages of Advantages and disadvantages of

DBMSs.DBMSs.

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Examples of Database Examples of Database ApplicationsApplications

Purchases from the supermarketPurchases from the supermarket Purchases using your credit cardPurchases using your credit card Booking a holiday at the travel agents Booking a holiday at the travel agents Using the local libraryUsing the local library Taking out insuranceTaking out insurance Using the InternetUsing the Internet Studying at universityStudying at university

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File-Based SystemsFile-Based Systems

Collection of application programs that Collection of application programs that perform services for the end users (e.g. perform services for the end users (e.g. reports). reports).

Each program defines and manages its Each program defines and manages its own data.own data.

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File-Based ProcessingFile-Based Processing

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Limitations of File-Based Limitations of File-Based ApproachApproach

Separation and isolation of dataSeparation and isolation of data Each program maintains its own set of data.Each program maintains its own set of data. Users of one program may be unaware of Users of one program may be unaware of

potentially useful data held by other programs.potentially useful data held by other programs.

Duplication of dataDuplication of data Same data is held by different programs.Same data is held by different programs. Wasted space and potentially different values Wasted space and potentially different values

and/or different formats for the same item.and/or different formats for the same item.

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Limitations of File-Based Limitations of File-Based ApproachApproach

Data dependenceData dependence File structure is defined in the program code.File structure is defined in the program code.

Incompatible file formatsIncompatible file formats Programs are written in different languages, and so cannot Programs are written in different languages, and so cannot

easily access each other’s files.easily access each other’s files.

Fixed Queries/Proliferation of application programsFixed Queries/Proliferation of application programs Programs are written to satisfy particular functions.Programs are written to satisfy particular functions. Any new requirement needs a new program.Any new requirement needs a new program.

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Database ApproachDatabase Approach

Arose because:Arose because: Definition of data was embedded in application Definition of data was embedded in application

programs, rather than being stored separately and programs, rather than being stored separately and independently.independently.

No control over access and manipulation of data No control over access and manipulation of data beyond that imposed by application programs.beyond that imposed by application programs.

Result:Result: the database and Database Management System the database and Database Management System

(DBMS).(DBMS).

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DatabaseDatabase

Shared collection of logically related data (and Shared collection of logically related data (and a description of this data), designed to meet the a description of this data), designed to meet the information needs of an organization.information needs of an organization.

System catalog (metadata) provides description System catalog (metadata) provides description of data to enable program–data independence.of data to enable program–data independence.

Logically related data comprises entities, Logically related data comprises entities, attributes, and relationships of an attributes, and relationships of an organization’s information.organization’s information.

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Database Management System Database Management System (DBMS)(DBMS)

A software system that enables users to A software system that enables users to define, create, and maintain the database define, create, and maintain the database and that provides controlled access to and that provides controlled access to this database.this database.

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Database Management System Database Management System (DBMS)(DBMS)

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Database ApproachDatabase Approach

Data definition language (DDL).Data definition language (DDL). Permits specification of data types, structures and Permits specification of data types, structures and

any data constraints. any data constraints. All specifications are stored in the database.All specifications are stored in the database.

Data manipulation language (DML).Data manipulation language (DML). General enquiry facility (query language) of the General enquiry facility (query language) of the

data.data.

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Database ApproachDatabase Approach

Controlled access to database may include:Controlled access to database may include: A security system.A security system. An integrity system.An integrity system. A concurrency control system.A concurrency control system. A recovery control system.A recovery control system. A user-accessible catalog.A user-accessible catalog.

A view mechanism.A view mechanism. Provides users with only the data they want or need to Provides users with only the data they want or need to

use.use.

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ViewsViews

Allows each user to have his or her own Allows each user to have his or her own view of the database.view of the database.

A view is essentially some subset of the A view is essentially some subset of the database.database.

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ViewsViews

Benefits include:Benefits include: Reduce complexity;Reduce complexity; Provide a level of security;Provide a level of security; Provide a mechanism to customize the appearance Provide a mechanism to customize the appearance

of the database;of the database; Present a consistent, unchanging picture of the Present a consistent, unchanging picture of the

structure of the database, even if the underlying structure of the database, even if the underlying database is changeddatabase is changed..

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Components of DBMS Components of DBMS EnvironmentEnvironment

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Components of DBMS Components of DBMS EnvironmentEnvironment

HardwareHardware Can range from a PC to a network of Can range from a PC to a network of

computers.computers. SoftwareSoftware

DBMS, operating system, network software (if DBMS, operating system, network software (if necessary) and also the application programs.necessary) and also the application programs.

DataData Used by the organization and a description Used by the organization and a description

of this data called the schema.of this data called the schema.

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Components of DBMS Components of DBMS EnvironmentEnvironment

ProceduresProcedures Instructions and rules that should be applied to Instructions and rules that should be applied to

the design and use of the database and DBMS.the design and use of the database and DBMS.

PeoplePeople

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Roles in the Database Roles in the Database EnvironmentEnvironment

Data AdministratorData Administrator ( (DADA)) Database Administrator (DBA)Database Administrator (DBA) Database Designers (Logical and Database Designers (Logical and

Physical)Physical) Application ProgrammersApplication Programmers End Users (naive and sophisticated)End Users (naive and sophisticated)

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History of Database SystemsHistory of Database Systems

First-generationFirst-generation Hierarchical and NetworkHierarchical and Network

Second generationSecond generation RelationalRelational

Third generationThird generation Object RelationalObject Relational Object-OrientedObject-Oriented

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Advantages of DBMSsAdvantages of DBMSs

Control of data redundancyControl of data redundancy Data consistencyData consistency More information from the same amount of More information from the same amount of

datadata Sharing of dataSharing of data Improved data integrityImproved data integrity Improved securityImproved security Enforcement of standardsEnforcement of standards Economy of scaleEconomy of scale

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Advantages of DBMSsAdvantages of DBMSs

Balanced conflicting requirementsBalanced conflicting requirements Improved data accessibility and Improved data accessibility and

responsivenessresponsiveness Increased productivityIncreased productivity Improved maintenance through data Improved maintenance through data

independenceindependence Increased concurrencyIncreased concurrency Improved backup and recovery servicesImproved backup and recovery services

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Disadvantages of DBMSsDisadvantages of DBMSs

ComplexityComplexity SizeSize Cost of DBMSCost of DBMS Additional hardware costsAdditional hardware costs Cost of conversionCost of conversion PerformancePerformance Higher impact of a failureHigher impact of a failure