Relational database oracle

RELATIONAL DATABASES

1. RELATIONAL DATABASE
BY
S.JAMUNA
ASSISTANT PROFESSOR
DEPARTMENT OF COMPUTER APPLICATIONS
BON SECOURS COLLEGE FOR WOMEN
THANJAVUR

2. RELATIONAL DATABASE
•Arelationaldatabaseisatypeofdatabasethatstores
andprovidesaccesstodatapointsthatarerelatedto
oneanother.
•Relationaldatabasesarebasedontherelational
model,anintuitive,straightforwardwayof
representingdataintables.
•Inarelationaldatabase,eachrowinthetableisa
recordwithauniqueIDcalledthekey.
•Thecolumnsofthetableholdattributesofthedata,
andeachrecordusuallyhasavalueforeachattribute,
makingiteasytoestablishtherelationshipsamong
datapoints.

3. RELATIONAL DATABASE
WhatisRDBMS?
•RDBMSstandsforRelationalDatabaseManagementSystem.
•RDBMSisthebasisforSQL,andforallmoderndatabase
systemslikeMSSQLServer,IBMDB2,Oracle,MySQL,and
MicrosoftAccess.
•ARelationaldatabasemanagementsystem(RDBMS)isa
databasemanagementsystem(DBMS)thatisbasedonthe
relationalmodelasintroducedbyE.F.Codd.

4. RELATIONAL DATABASE
Relational database terms:
Tables
•ThedatainanRDBMSisstoredindatabase
objectswhicharecalledastables.Thistableis
basicallyacollectionofrelateddataentries
anditconsistsofnumerouscolumnsand
rows.

5. RELATIONAL DATABASE
Field:
•Everytableisbrokenupintosmallerentitiescalled
fields.ThefieldsintheCUSTOMERStableconsistof
ID,NAME,AGE,ADDRESSandSALARY.
•Afieldisacolumninatablethatisdesignedto
maintainspecificinformationabouteveryrecordin
thetable.

6. RELATIONAL DATABASE
RecordoraRow:
•Arecordisalsocalledasarowofdataiseach
individualentrythatexistsinatable.
Column:
•Acolumnisaverticalentityinatablethatcontains
allinformationassociatedwithaspecificfieldina
table.

7. RELATIONAL DATABASE
NULL value:
•ANULLvalueinatableisavalueinafieldthat
appearstobeblank,whichmeansafieldwithaNULL
valueisafieldwithnovalue.
•ItisveryimportanttounderstandthataNULLvalue
isdifferentthanazerovalueorafieldthatcontains
spaces.AfieldwithaNULLvalueistheonethathas
beenleftblankduringarecordcreation.

8. RELATIONAL DATABASE
ADVANTAGES & DISADVANTAGES
•Advantages:
1.Easeofuse:Therevisionofanyinformationastablesconsistingofrows
andcolumnsismucheasiertounderstand.
2.Flexibility:Differenttablesfromwhichinformationhastobelinkedand
extractedcanbeeasilymanipulatedbyoperatorssuchasprojectandjointo
giveinformationintheforminwhichitisdesired.
3.Precision:Theusageofrelationalalgebraandrelationalcalculusinthe
manipulationofherelationsbetweenthetablesensuresthatthereisno
ambiguity,whichmayotherwiseariseinestablishingthelinkagesina
complicatednetworktypedatabase.

9. RELATIONAL DATABASE
4.Security:Securitycontrolandauthorizationcanalsobeimplementedmore
easilybymovingsensitiveattributesinagiventableintoaseparaterelation
withitsownauthorizationcontrols.Ifauthorizationrequirementpermits,a
particularattributecouldbejoinedbackwithotherstoenablefull
informationretrieval.
5.DataIndependence:Dataindependenceisachievedmoreeasilywith
normalizationstructureusedinarelationaldatabasethaninthemore
complicatedtreeornetworkstructure.
6.DataManipulationLanguage:Thepossibilityofrespondingtoqueryby
meansofalanguagebasedonrelationalalgebraandrelationalcalculuse.g
SQLiseasyintherelationaldatabaseapproach.Fordataorganizedinother
structurethequerylanguageeitherbecomescomplexorextremelylimitedin
itscapabilities.

10. RELATIONAL DATABASE
•Disadvantages:
1.Performance:Amajorconstraintandthereforedisadvantageintheuseof
relationaldatabasesystemismachineperformance.Ifthenumberoftables
betweenwhichrelationshipstobeestablishedarelargeandthetables
themselveseffecttheperformanceinrespondingtothesqlqueries.
2.PhysicalStorageConsumption:Withaninteractivesystem,forexamplean
operationlikejoinwoulddependuponthephysicalstoragealso.Itis,
thereforecommoninrelationaldatabasestotunethedatabasesandinsuch
acasethephysicaldatalayoutwouldbechosensoastogivegood
performanceinthemostfrequentlyrunoperations.Itthereforewould
naturallyresultinthefactthatthelaysfrequentlyrunoperationswouldtend
tobecomeevenmoreshared.
3.Slowextractionofmeaningfromdata:ifthedataisnaturallyorganizedina
hierarchicalmannerandstoredassuch,thehierarchicalapproachmaygive
quickmeaningforthatdata.

11. THANK YOU