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Unit IIIUnit III -- Chapter 5Chapter 5

Logical Database DesignLogical Database Design

and theand the

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Relational Database Model

Represents data in the form of tables.

Consists of three components: Data strctre ! "ables with rows and colmns

Data Maniplation Data #ntegrit$

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Re ationRe ation AA relationrelation isis aa named&named& twotwo''dimensionaldimensional tabletable ofof datadata

"able"able consistsconsists ofof rowsrows (records)(records) andand colmnscolmns (attribte(attribteoror field)field)

Re*irementsRe*irements forfor aa tabletable toto *alif$*alif$ asas aa relationrelation::

#t#t mstmst ha+eha+e aa ni*eni*e namename ,+er$,+er$ attribteattribte +ale+ale mstmst bebe atomicatomic (not(not mltimlti''

+aled&+aled& notnot composite)composite)

,+er$,+er$ rowrow mstmst bebe ni*eni*e (can-t(can-t ha+eha+e twotwo rowsrowswithwith eactl$eactl$ thethe samesame +ales+ales forfor allall theirtheir fields)fields)

AttribtesAttribtes (colmns)(colmns) inin tablestables mstmst ha+eha+e ni*eni*e

/

namesnames "he"he orderorder ofof thethe colmnscolmns mstmst bebe irrele+antirrele+ant

"he"he orderorder ofof thethe rowsrows mstmst bebe irrele+antirrele+ant

AlsoAlso calledcalled thethe 11stst NormalNormal FormFormMohit Agrawal @GU

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#s this a relation00

Employee_ID Name Department Course Age

122 A 3

4544&

Research

$rs&months& 1%

da$s

162 7 8 "a& 9a+a

/% $ears&

months& %6

da$s

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162 7 8 "a

&

months& %6da$s

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Con+ersion to Relation...

Employee

ID Name Department Course Age_Year

Age_o

nths Age_Days

_

122 A 3 4544 % / 1%

122 A 3 Research % / 1%

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162 7 8 "a /% %6

162 7 8 9a+a /% %6

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QuestionIs this a relation?AnswerYes: Unique rows and no

multivalued attributes

QuestionWhats the primary key? AnswerComposite: Emp_ID, Course_Title

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Correspondence with ,Correspondence with ,''R ModelR Model Relations (tables) correspond with entit$ t$pesRelations (tables) correspond with entit$ t$pes

Rows correspond with entit$ instancesRows correspond with entit$ instances

Colmns correspond with attribtesColmns correspond with attribtes

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>e$ ?ields>e$ ?ields >e$s>e$s areare specialspecial fieldsfields thatthat ser+eser+e twotwo mainmain prposesprposes::

PrimaryPrimary keyskeys areare ni*eni*e identifiersidentifiers ofof thethe relationrelation ininestionestion..

,amples,amples incldeinclde emplo$eeemplo$ee nmbers&nmbers& socialsocial secrit$secrit$nmbers&nmbers& etcetc.. ThisThis isis howhow wewe cancan guaranteeguarantee thatthat allallrowsrows areare uniqueunique

RelationshipsRelationships betweenbetween relationsrelations isis accomplishedaccomplished throghthroghForeignForeign keyskeys..

ForeignForeign KeyKey isis anan attribteattribte inin aa relationrelation thatthat ser+esser+es asas aa

primar$primar$ e$e$ oo anot eranot er re ationre ation

>e$s>e$s cancan bebe simplesimple (a(a singlesingle field)field) oror compositecomposite (more(more thanthanoneone field)field)

>e$s>e$s sall$sall$ areare sedsed asas indeesindees toto speedspeed pp thethe responseresponse toto

serser *eries*eriesMohit Agrawal @GU

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Relational 4chema

Foreign Key

B

Composite primary key

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=becti+es=becti+es

Con+ertCon+ert anan ,R,R DiagramDiagram toto RelationalRelational 4chema4chema

forfor frtherfrther implementationimplementation

LearnLearn thethe processprocess ofof

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Integrity ConstraintsIntegrity Constraints

datadata inin aa databasedatabase

DomainDomain ConstraintsConstraints

,ntit$,ntit$ #ntegrit$#ntegrit$

ReferentialReferential #ntegrit$#ntegrit$

11

ActionAction AssertionsAssertions FF 7siness7siness rlesrles..

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Domain Constraints

Domain is the possible set of +ales that ma$

e ass gne o an$ a r e

Attri!ute Domain Name Description Domain

Customer_ID Customer_IDs "et o# all possi!le

customer IDs Character$ si%e 5

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Customer_Name Customer_Names "et o# all possi!le

customer Names Character$ si%e &5

City Cities "et o# all possi!le

cities

Character$ si%e &'

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Entity Integrity

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Referential #ntegrit$

Customer_

ID Name Address City "tate (ostal_Code

1222 A A7C Delhi Delhi 1%/6;

1221 7 38 Mmbai Maharashtra 1%;6/

122% C 4"U

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Referential #ntegrit$

"ables"ables areare associatedassociated singsing ?oreign?oreign >e$s>e$s

ReferentialReferential #ntegrit$#ntegrit$ rlerle statesstates thatthat ifif therethere isisaa foreignforeign e$e$ inin oneone relation&relation&

eithereither eacheach foreignforeign e$e$ +ale+ale mstmst matchmatch aaprimar$primar$ e$e$ +ale+ale inin anotheranother relationrelation (Mandator$(Mandator$

relations)orrelations)or

thethe foreignforeign e$e$ mstmst bebe

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Referential

integrity

constraints aredrawn via arrows

from dependent to

1

parent ta e

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7siness Rles7siness Rles

4tatements4tatements thatthat definedefine oror constrainconstrain somesome

aspecaspec oo ee s nesss ness AssertAssert bsinessbsiness strctrestrctre

ControlFinflenceControlFinflence bsinessbsiness beha+iorbeha+ior ,pressed,pressed inin termsterms familiarfamiliar toto endend serssers

1

AtomatedAtomated throghthrogh D7M4D7M4 softwaresoftware

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,ell,ell--"tructured +elations"tructured +elations

AA relationrelation thatthat containscontains minimalminimal datadataredndanc$redndanc$ andand allowsallows serssers toto insert&insert&deletedelete andand date date rowsrows withotwithot casincasin

datadata inconsistenciesinconsistencies

GoalGoal isis toto a+oida+oid anomaliesanomalies

InsertionInsertion AnomalyAnomaly!!addingadding newnew rowsrows forcesforcesserser toto createcreate dplicatedplicate datadata

DeletionDeletion AnomalAnomal !!deletindeletin rowsrows mama casecase aa

1

lossloss ofof datadata thatthat woldwold bebe neededneeded forfor otherotherftreftre rowsrows

odi#icationodi#ication AnomalyAnomaly!!changingchanging datadata inin aa rowrow

forcesforces changeschanges toto otherother rowsrows becasebecase ofofdplicationdplication Mohit Agrawal @GU

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InsertionInsertion!!can-t enter a new emplo$ee withot ha+ing thecan-t enter a new emplo$ee withot ha+ing the

em lo ee tae a classem lo ee tae a class

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DeletionDeletion!!if we remo+e emplo$ee 162& we lose informationif we remo+e emplo$ee 162& we lose informationabot the eistence of a "a Acc classabot the eistence of a "a Acc class

odi#icationodi#ication!!gi+ing a salar$ increase to emplo$ee 122 forcesgi+ing a salar$ increase to emplo$ee 122 forces

s to pdate mltiple recordss to pdate mltiple records

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Data Normali%ationData Normali%ation

5rimaril$5rimaril$ aa tooltool toto +alidate+alidate andand impro+eimpro+e aalogicallogical designdesign soso thatthat itit satisfiessatisfies certaincertain

cons ra n scons ra n s aa avoavo unnecessaryunnecessaryduplicationduplication ofof datadata

"he"he processprocess ofof decomposingdecomposing relationsrelations withwithanomaliesanomalies toto prodceprodce smaller&smaller&wellwell--structuredstructured

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4teps in Con+ersion

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4teps in Con+ersion

4",5 1 ! Map Reglar ,ntities Composite Attribtes

Mlti'Haled Attribtes

4",5 % ! Map ea ,ntities 4",5 / ! Map 7inar$ Relationships

=ne to Man$

Man$ to Man$

=ne to =ne

4",5 6 ! Map Associati+e ,ntities

4",5 ; ! Map Unar$ Relationships

4",5 ! Map ternar$ Relationships

Mohit Agrawal @GU %%