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CHAPTER 2:CHAPTER 2:MODELING DATA IN THEMODELING DATA IN THE

ORGANIZATIONORGANIZATION

2013 Pearson Educa!on" Inc# Pu%&!s'!n( as Pren!ceHa&&

1

Modern Database Management

11thEdition

Jefrey A. Hofer, V. Ramesh,

Heikki Topi


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Chapter 2 2013 Pearson Education, Inc. Publishing as Prentice Hall 2013 Pearson Education, Inc. Publishing as Prentice Hall

O)*ECTI+E,O)*ECTI+E,

De-ne er.sDe-ne er.s /ndersand !.orance o daa .ode&!n(/ndersand !.orance o daa .ode&!n( r!e (ood na.es and de-n!!ons or en!!es"r!e (ood na.es and de-n!!ons or en!!es"

re&a!ons'!s" and ar!%uesre&a!ons'!s" and ar!%ues

D!s!n(u!s' unar" %!nar" and ernar re&a!ons'!sD!s!n(u!s' unar" %!nar" and ernar re&a!ons'!s Mode& d!4eren es o ar!%ues" en!!es"Mode& d!4eren es o ar!%ues" en!!es"

re&a!ons'!s" and card!na&!!esre&a!ons'!s" and card!na&!!es Dra5 E6R d!a(ra.s or co..on %us!ness s!ua!onsDra5 E6R d!a(ra.s or co..on %us!ness s!ua!ons

Con7er .an6o6.an re&a!ons'!s o assoc!a!7eCon7er .an6o6.an re&a!ons'!s o assoc!a!7een!!esen!!es Mode& !.e6deenden daa us!n( !.e sa.sMode& !.e6deenden daa us!n( !.e sa.s

2


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A GOOD DATA NAME I,:A GOOD DATA NAME I,:

Re&aed o %us!ness" no ec'n!ca&"Re&aed o %us!ness" no ec'n!ca&"

c'aracer!s!csc'aracer!s!cs

Mean!n(u& and se&6docu.en!n(Mean!n(u& and se&6docu.en!n(

/n!8ue/n!8ue

Reada%&eReada%&e

Co.osed o 5ords ro. an aro7ed &!sCo.osed o 5ords ro. an aro7ed &!s

Reeaa%&eReeaa%&e r!en !n sandard sna9r!en !n sandard sna9

3


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DATA DEINITION,DATA DEINITION,

E9&ana!on o a er. or acE9&ana!on o a er. or ac Ter.;5ord or 'rase 5!' sec!-c .ean!n(Ter.;5ord or 'rase 5!' sec!-c .ean!n(

ac;assoc!a!on %e5een 5o or .ore er.sac;assoc!a!on %e5een 5o or .ore er.s

Gu!de&!nes or (ood daa de-n!!onGu!de&!nes or (ood daa de-n!!on A conc!se descr!!on o essen!a& daa .ean!n(A conc!se descr!!on o essen!a& daa .ean!n(

Ga'ered !n con


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E6R MODELE6R MODEL CON,TR/CT,CON,TR/CT,

En!!es:En!!es: En! !nsance;erson" &ace" o%oen corresonds o a ro5 !n a a%&e? En! Te;co&&ec!on o en!!es >oen corresonds o aEn! Te;co&&ec!on o en!!es >oen corresonds o a

a%&e?a%&e?

Re&a!ons'!s:Re&a!ons'!s: Re&a!ons'! !nsance;&!n@ %e5een en!!es >corresondsRe&a!ons'! !nsance;&!n@ %e5een en!!es >corresonds

o r!.ar @e6ore!(n @e e8u!7a&enc!es !n re&aed a%&es?o r!.ar @e6ore!(n @e e8u!7a&enc!es !n re&aed a%&es? Re&a!ons'! e;cae(or o re&a!ons'!&!n@ %e5eenRe&a!ons'! e;cae(or o re&a!ons'!&!n@ %e5een

en! esen! es Ar!%ues:Ar!%ues:

Proer!es or c'aracer!s!cs o an en! or re&a!ons'!Proer!es or c'aracer!s!cs o an en! or re&a!ons'!e >oen corresonds o a -e&d !n a a%&e?e >oen corresonds o a -e&d !n a a%&e?

B


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Sample E! "iagram #$igure 21%



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!elationship

degrees

speci&' number

o& entit' t'pesin(ol(ed

Entit's'mbols

) special entit'

that is also a

relationship

!elationship

s'mbols

!elationshipcardinalities

speci&' ho*

man' o& each

entit' t'pe is

allo*ed

)ttribute

s'mbols

+asic E! notation #$igure 22%



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)/,INE,, R/LE,)/,INE,, R/LE,

Are sae.ens 'a de-ne or consra!nAre sae.ens 'a de-ne or consra!n

so.e asec o 'e %us!nessso.e asec o 'e %us!ness

Are der!7ed ro. o&!c!es" rocedures"Are der!7ed ro. o&!c!es" rocedures"

e7ens" unc!onse7ens" unc!ons Asser %us!ness srucureAsser %us!ness srucure

Conro&!nFuence %us!ness %e'a7!orConro&!nFuence %us!ness %e'a7!or

Are e9ressed !n er.s a.!&!ar o end usersAre e9ressed !n er.s a.!&!ar o end users Are auo.aed 'rou(' D)M, so5areAre auo.aed 'rou(' D)M, so5are


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A GOOD )/,INE,, R/LE I,:A GOOD )/,INE,, R/LE I,:

Dec&ara!7e;5'a" no 'o5Dec&ara!7e;5'a" no 'o5 Prec!se;c&ear" a(reed6uon .ean!n(Prec!se;c&ear" a(reed6uon .ean!n( Ao.!c;one sae.enAo.!c;one sae.en Cons!sen;!nerna&& and e9erna&&Cons!sen;!nerna&& and e9erna&& E9ress!%&e;srucured" naura&E9ress!%&e;srucured" naura&

&an(ua(e&an(ua(e

D!s!nc;non6redundanD!s!nc;non6redundan )us!ness6or!ened;undersood %)us!ness6or!ened;undersood %

%us!ness eo&e%us!ness eo&e


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ENTITIE,ENTITIE,

EntityEntity; a erson" a &ace" an; a erson" a &ace" ano%


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ENTITJ TJPE AND ENTITJENTITJ TJPE AND ENTITJ

IN,TANCE,IN,TANCE,

11


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AN ENTITJAN ENTITJ

,HO/LD )E:,HO/LD )E: An o%


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Inappropriate

entities

SystemSystem

useruser

SystemSystem

outputoutput

$igure 2 E-ample o& inappropriate entities

)ppropriate

entities


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,TRONG +,# EAK ENTITIE,",TRONG +,# EAK ENTITIE,"

ANDANDIDENTIJING RELATION,HIP,IDENTIJING RELATION,HIP, ,ron( en!,ron( en! e9!ss !ndeenden& o o'er es o en!!ese9!ss !ndeenden& o o'er es o en!!es 'as !s o5n un!8ue !den!-er'as !s o5n un!8ue !den!-er

!den!-er under&!ned 5!' s!n(&e &!ne!den!-er under&!ned 5!' s!n(&e &!ne

ea@ en!ea@ en! deenden on a sron( en! >!den!!n( o5ner?canno e9!s ondeenden on a sron( en! >!den!!n( o5ner?canno e9!s on!s o5n!s o5n

does no 'a7e a un!8ue !den!-er >on& a ar!a& !den!-er?does no 'a7e a un!8ue !den!-er >on& a ar!a& !den!-er? en! %o9 and ar!a& !den!-er 'a7e dou%&e &!nesen! %o9 and ar!a& !den!-er 'a7e dou%&e &!nes

Iden!!n( re&a!ons'!Iden!!n( re&a!ons'! &!n@s sron( en!!es o 5ea@ en!!es&!n@s sron( en!!es o 5ea@ en!!es

1=


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Strong entit' ea/ entit'

$igure 2 E-ample o& a *ea/ identit' and its identi&'ing relationship


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ATTRI)/TE,ATTRI)/TE,

Ar!%ue;roer or c'aracer!s!c oAr!%ue;roer or c'aracer!s!c oan en! or re&a!ons'! ean en! or re&a!ons'! e

C&ass!-ca!ons o ar!%ues:C&ass!-ca!ons o ar!%ues:

Re8u!red 7ersus O!ona& Ar!%uesRe8u!red 7ersus O!ona& Ar!%ues ,!.&e 7ersus Co.os!e Ar!%ue,!.&e 7ersus Co.os!e Ar!%ue ,!n(&e6+a&ued 7ersus Mu&!7a&ued Ar!%ue,!n(&e6+a&ued 7ersus Mu&!7a&ued Ar!%ue ,ored 7ersus Der!7ed Ar!%ues,ored 7ersus Der!7ed Ar!%ues Iden!-er Ar!%uesIden!-er Ar!%ues

1


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RE/IRED +,# OPTIONALRE/IRED +,# OPTIONAL


1

Required; .us 'a7e a 7a&ue ore7er en! >or re&a!ons'!?!nsance 5!' 5'!c' ! !s assoc!aed

Optional; .a no 'a7e a 7a&ueor e7er en! >or re&a!ons'!?!nsance 5!' 5'!c' ! !s assoc!aed


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,IMPLE +,# COMPO,ITE,IMPLE +,# COMPO,ITE


Composite attributeComposite attribute; An ar!%ue 'a 'as; An ar!%ue 'a 'as.ean!n(u& co.onen ars >ar!%ues?.ean!n(u& co.onen ars >ar!%ues?

1

The address is

broken into

component parts

$igure 2 ) compositeattribute


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1

$igure 2 Entit' *ith multivaluedattribute #S/ill% and derivedattribute

#ears Emplo'ed%

Multivaluedan e.&oee can'a7e .ore 'anone s@!&&

DerivedCa&cu&aedro. daee.&oedandcurren

dae

Mu&!67a&ued and Der!7edMu&!67a&ued and Der!7ed

Ar!%uesAr!%uesMultivalued ; .a a@e on .ore'an one 7a&ue or a (!7en en! >orre&a!ons'!? !nsance

Derived ; 7a&ues can %e ca&cu&aedro. re&aed ar!%ue 7a&ues >no's!ca&& sored !n 'e daa%ase?

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IDENTIIER, >KEJ,?IDENTIIER, >KEJ,?

Iden!-er >Ke?;an ar!%ue >orIden!-er >Ke?;an ar!%ue >orco.%!na!on o ar!%ues? 'aco.%!na!on o ar!%ues? 'aun!8ue& !den!-es !nd!7!dua&un!8ue& !den!-es !nd!7!dua&

!nsances o an en! e!nsances o an en! e ,!.&e 7ersus Co.os!e Iden!-er,!.&e 7ersus Co.os!e Iden!-er Cand!dae Iden!-er;an ar!%ueCand!dae Iden!-er;an ar!%ue

'a cou&d %e a @esa!s-es 'e'a cou&d %e a @esa!s-es 'ere8u!re.ens or %e!n( an !den!-erre8u!re.ens or %e!n( an !den!-er

20


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CRITERIA OR IDENTIIER,CRITERIA OR IDENTIIER,

C'oose Iden!-ers 'aC'oose Iden!-ers 'a !&& no c'an(e !n 7a&ue!&& no c'an(e !n 7a&ue

!&& no %e nu&&!&& no %e nu&&

A7o!d !ne&&!(en !den!-ers >e#(#" cona!n!n(A7o!d !ne&&!(en !den!-ers >e#(#" cona!n!n(&oca!ons or eo&e 'a .!(' c'an(e?&oca!ons or eo&e 'a .!(' c'an(e?

,u%s!ue ne5" s!.&e @es or &on(",u%s!ue ne5" s!.&e @es or &on("

co.os!e @esco.os!e @es

21


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22

$igure 24 Simple and composite identi&ier attributes

5he identi&ieris bold&aced

and underlined



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NAMING ATTRI)/TE,NAMING ATTRI)/TE,

Na.e s'ou&d %e a s!n(u&ar noun or nounNa.e s'ou&d %e a s!n(u&ar noun or noun'rase'rase

Na.e s'ou&d %e un!8ueNa.e s'ou&d %e un!8ue

Na.e s'ou&d o&&o5 a sandard or.aNa.e s'ou&d o&&o5 a sandard or.a e#(#e#(# [Entity type name { [ Qualifer ] } ] Class[Entity type name { [ Qualifer ] } ] Class

,!.!&ar ar!%ues o d!4eren en! es,!.!&ar ar!%ues o d!4eren en! es

s'ou&d use 'e sa.e 8ua&!-ers and c&assess'ou&d use 'e sa.e 8ua&!-ers and c&asses

23


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DEINING ATTRI)/TE,DEINING ATTRI)/TE,

,ae 5'a 'e ar!%ue !s and oss!%& 5' ! !s,ae 5'a 'e ar!%ue !s and oss!%& 5' ! !s

!.oran!.oran

Ma@e ! c&ear 5'a !s and !s no !nc&uded !n 'e ar!%uesMa@e ! c&ear 5'a !s and !s no !nc&uded !n 'e ar!%ues

7a&ue7a&ue

Inc&ude a&!ases !n docu.ena!onInc&ude a&!ases !n docu.ena!on ,ae source o 7a&ues,ae source o 7a&ues

,ec! re8u!red 7s# o!ona&,ec! re8u!red 7s# o!ona&

,ae .!n and .a9 nu.%er o occurrences a&&o5ed,ae .!n and .a9 nu.%er o occurrences a&&o5ed

Ind!cae re&a!ons'!s 5!' o'er ar!%uesInd!cae re&a!ons'!s 5!' o'er ar!%ues

2=


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MODELING RELATION,HIP,MODELING RELATION,HIP,

Re&a!ons'! Tes 7s# Re&a!ons'! InsancesRe&a!ons'! Tes 7s# Re&a!ons'! Insances T'e re&a!ons'! e !s .ode&ed as &!nes %e5eenT'e re&a!ons'! e !s .ode&ed as &!nes %e5een

en! es'e !nsance !s %e5een sec!-c en!en! es'e !nsance !s %e5een sec!-c en!!nsances!nsances

Re&a!ons'!s can 'a7e ar!%uesRe&a!ons'!s can 'a7e ar!%ues T'ese descr!%e eaures era!n!n( o 'e assoc!a!on %e5eenT'ese descr!%e eaures era!n!n( o 'e assoc!a!on %e5een

'e en!!es !n 'e re&a!ons'!'e en!!es !n 'e re&a!ons'!

T5o en!!es can 'a7e .ore 'an one e oT5o en!!es can 'a7e .ore 'an one e ore&a!ons'! %e5een 'e. >.u&!&ere&a!ons'! %e5een 'e. >.u&!&ere&a!ons'!s?re&a!ons'!s?

Assoc!a!7e En!;co.%!na!on o re&a!ons'!Assoc!a!7e En!;co.%!na!on o re&a!ons'!and en!and en!

2B


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2

!(ure 2610 Re&a!ons'! es and !nsances

a? Re&a!ons'!e>Co.&ees?

%?Re&a!ons'!!nsances



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DEGREE O RELATION,HIP,DEGREE O RELATION,HIP,

De(ree o a re&a!ons'! !sDe(ree o a re&a!ons'! !s'e nu.%er o en! es'e nu.%er o en! es

'a ar!c!ae !n !'a ar!c!ae !n ! /nar Re&a!ons'!/nar Re&a!ons'! )!nar Re&a!ons'!)!nar Re&a!ons'!Ternar Re&a!ons'!Ternar Re&a!ons'!

2


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2

"egree o& relationships 6 &rom $igure 22

Entities of

two different

types relatedto each other

Entities of threedifferent types

related to each

other

One entity

related toanother of

the same

entity type



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CARDINALITJ O RELATION,HIP,CARDINALITJ O RELATION,HIP,

One6o6OneOne6o6One Eac' en! !n 'e re&a!ons'! 5!&& 'a7e e9ac&Eac' en! !n 'e re&a!ons'! 5!&& 'a7e e9ac&

one re&aed en!one re&aed en!

One6o6ManOne6o6Man An en! on one s!de o 'e re&a!ons'! canAn en! on one s!de o 'e re&a!ons'! can

'a7e .an re&aed en!!es" %u an en! on 'e'a7e .an re&aed en!!es" %u an en! on 'eo'er s!de 5!&& 'a7e a .a9!.u. o one re&aedo'er s!de 5!&& 'a7e a .a9!.u. o one re&aeden!en!

Man6o6ManMan6o6Man En!!es on %o' s!des o 'e re&a!ons'! canEn!!es on %o' s!des o 'e re&a!ons'! can

'a7e .an re&aed en!!es on 'e o'er s!de'a7e .an re&aed en!!es on 'e o'er s!de

2


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30

!(ure 2612 E9a.&es o re&a!ons'!s o d!4eren de(rees

a? /nar re&a!ons'!s



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31

!(ure 2612 E9a.&es o re&a!ons'!s o d!4eren de(rees >con#?

%? )!nar re&a!ons'!s



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32

!(ure 2612 E9a.&es o re&a!ons'!s o d!4eren de(rees >con#?

c? Ternar re&a!ons'!

Note: a relationship can have attributes of its own



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CARDINALITJ CON,TRAINT,CARDINALITJ CON,TRAINT,

Card!na&! Consra!ns'e nu.%er oCard!na&! Consra!ns'e nu.%er o!nsances o one en! 'a can or .us!nsances o one en! 'a can or .us%e assoc!aed 5!' eac' !nsance o%e assoc!aed 5!' eac' !nsance oano'er en!ano'er en!

M!n!.u. Card!na&!M!n!.u. Card!na&! I ero" 'en o!ona&I ero" 'en o!ona& I one or .ore" 'en .andaorI one or .ore" 'en .andaor

Ma9!.u. Card!na&!Ma9!.u. Card!na&! T'e .a9!.u. nu.%erT'e .a9!.u. nu.%er

33


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3=

!(ure 261 E9a.&es o card!na&! consra!ns

a% 7andator' cardinalities

A a!en .us 'a7erecorded a &eas one'!sor" and can 'a7e.an

A a!en '!sor !srecorded or one andon& one a!en

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3B

!(ure 261 E9a.&es o card!na&! consra!ns >con#?

b% 8ne optional, one mandator'

An e.&oee can %eass!(ned o an nu.%ero ro


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3

!(ure 261 E9a.&es o card!na&! consra!ns >con#?

c% 8ptional cardinalities

A erson !s.arr!ed o a.os one o'ererson" or .a

no %e .arr!eda a&&



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3

Entities can be related to one another in more than one *a'

!(ure 2621 E9a.&es o .u&!&e re&a!ons'!s

a% Emplo'ees and departments



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3

!(ure 2621 E9a.&es o .u&!&e re&a!ons'!s >con#?

b% Pro&essors and courses #&i-ed lo*er limit constraint%

Here, min cardinalit' constraint is 2. )t least t*opro&essors must be 9uali&ied to teach each course. Each

pro&essor must be 9uali&ied to teach at least one course.


! 2 1B d 2 1B% M & ! & d !% % d & !


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3

!(ure 261Ba and 261B% Mu&!7a&ued ar!%ues can %e reresened as re&a!on

s!.&e

co.os!e



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A,,OCIATI+E ENTITIE,A,,OCIATI+E ENTITIE, An en!;'as ar!%uesAn en!;'as ar!%ues A re&a!ons'!;&!n@s en!!es o(e'erA re&a!ons'!;&!n@s en!!es o(e'er 'en s'ou&d a'en s'ou&d a relationship with attributesrelationship with attributes!nsead %e an!nsead %e an

associative entityassociative entity A&& re&a!ons'!s or 'e assoc!a!7e en! s'ou&d %e .anA&& re&a!ons'!s or 'e assoc!a!7e en! s'ou&d %e .an

T'e assoc!a!7e en! cou&d 'a7e .ean!n( !ndeenden o 'eT'e assoc!a!7e en! cou&d 'a7e .ean!n( !ndeenden o 'eo'er en!!eso'er en!!es T'e assoc!a!7e en! reera%& 'as a un!8ue !den!-er" andT'e assoc!a!7e en! reera%& 'as a un!8ue !den!-er" and

s'ou&d a&so 'a7e o'er ar!%uess'ou&d a&so 'a7e o'er ar!%ues T'e assoc!a!7e en! .a ar!c!ae !n o'er re&a!ons'!sT'e assoc!a!7e en! .a ar!c!ae !n o'er re&a!ons'!s

o'er 'an 'e en!!es o 'e assoc!aed re&a!ons'!o'er 'an 'e en!!es o 'e assoc!aed re&a!ons'! Ternar re&a!ons'!s s'ou&d %e con7ered o assoc!a!7e en!!esTernar re&a!ons'!s s'ou&d %e con7ered o assoc!a!7e en!!es

=0


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=1

!(ure 2611a A %!nar re&a!ons'! 5!' an ar!%ue

Here, the date completed attribute pertains speci&icall' to theemplo'ee:s completion o& a course;it is an attribute o& the

relationship.

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=2

!(ure 2611% An assoc!a!7e en! >CERTIICATE?

)ssociati(e entit' is li/e a relationship *ith an attribute, but it is

also considered to be an entit' in its o*n right.


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=3

!(ure 2613c An assoc!a!7e en! ; %!&& o .aer!a&s sr

5his could =ust be a relationship *ith

attributes;it:s a =udgment call.

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==

!(ure 261 Card!na&! consra!ns !n a ernar re&a!ons

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=B

$igure 214 Simple e-ample o& timestamping

T'e Pr!ce H!sorar!%ue !s %o'.u&!7a&ued andco.os!e#

ime stamp; a !.e 7a&ue 'a !sassoc!aed 5!' a daa 7a&ue" oen!nd!ca!n( 5'en so.e e7en occurred'a a4eced 'e daa 7a&ue

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=

$igure 220c E! diagram *ith associati(e entit' &or

product assignment to product line o(er time

T'e Ass!(n.enassoc!a!7e en!s'o5s 'e dae ran(eo a roducsass!(n.en o aar!cu&ar roduc &!ne#

Mode&!n( !.e6deenden daa 'as%eco.e .ore !.oran due ore(u&a!ons suc' as HIPAA and,ar%anes6O9&e#

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=

!(ure 2622Daa .ode& orP!ne +a&&e

urn!ureCo.an !nM!croso +!s!onoa!on

D!4eren .ode&!n(so5are oo&s .a'a7e d!4erennoa!on or 'e sa.e

consrucs#

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Cor!(' 2013 Pearson Educa!on" Inc# Pu%&!s'!n( as Pren!ceCor!(' 2013 Pearson Educa!on" Inc# Pu%&!s'!n( as Pren!ce

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Hoffer Mdm11e Pp Ch02