数据库系统基础教程第二章答案终审稿Word文档下载推荐.docx
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type,
balance
）
Customers（
firstName,
lastName,
idNo,
account
Asuitabledomainforeachattribute:
acctNoInteger
typeString
balanceInteger
firstNameString
lastNameString
idNoString（becausethereisahyphenwecannotuseInteger）
accountInteger
AnotherequivalentwaytopresenttheAccountrelation:
acctNo
balance
type
34567
25
savings
23456
1000
checking
12345
12000
AnotherequivalentwaytopresenttheCustomersrelation:
idNo
firstName
lastName
account
805-333
Lena
Hand
901-222
Robbie
Banks
Exercise2.2.2
Examplesofattributesthatarecreatedforprimarilyservingaskeysinarelation:
UniversalProductCode（UPC）usedwidelyinUnitedStatesandCanadatotrackproductsinstores.
SerialNumbersonawidevarietyofproductstoallowthemanufacturertoindividuallytrackeachproduct.
VehicleIdentificationNumbers（VIN）,auniqueserialnumberusedbytheautomotiveindustrytoidentifyvehicles.
Wecanorderthethreetuplesinanyof3!
=6ways.Also,thecolumnscanbeorderedinanyof3!
=6ways.Thus,thenumberofpresentationsis6*6=36.
Wecanorderthethreetuplesinanyof5!
=120ways.Also,thecolumnscanbeorderedinanyof4!
=24ways.Thus,thenumberofpresentationsis120*24=2880
Wecanorderthethreetuplesinanyofm!
ways.Also,thecolumnscanbeorderedinanyofn!
ways.Thus,thenumberofpresentationsisn!
m!
CREATETABLEProduct（
makerCHAR（30）,
modelCHAR（10）PRIMARYKEY,
typeCHAR（15）
）;
CREATETABLEPC（
modelCHAR（30）,
speedDECIMAL（4,2）,
ramINTEGER,
hdINTEGER,
priceDECIMAL（7,2）
CREATETABLELaptop（
screenDECIMAL（3,1）,
CREATETABLEPrinter（
colorBOOLEAN,
typeCHAR（10）,
ALTERTABLEPrinterDROPcolor;
ALTERTABLELaptopADDodCHAR（10）DEFAULT‘none’;
CREATETABLEClasses（
classCHAR（20）,
typeCHAR（5）,
countryCHAR（20）,
numGunsINTEGER,
boreDECIMAL（3,1）,
displacementINTEGER
CREATETABLEShips（
nameCHAR（30）,
launchedINTEGER
CREATETABLEBattles（
dateDATE
CREATETABLEOutcomes（
shipCHAR（30）,
battleCHAR（30）,
resultCHAR（10）
ALTERTABLEClassesDROPbore;
ALTERTABLEShipsADDyardCHAR（30）;
R1:
=σspeed≥3.00（PC）
R2:
=πmodel（R1）
model
1005
1006
1013
=σhd≥100（Laptop）
=Product
（R1）
R3:
=πmaker（R2）
maker
E
A
B
F
G
=σmaker=B（Product
PC）
Laptop）
Printer）
R4:
=πmodel,price（R1）
R5:
=πmodel,price（R2）
R6:
=πmodel,price（R3）
R7:
=R4
R5
R6
price
1004
649
630
1049
2007
1429
=σcolor=trueANDtype=laser（Printer）
=πmodel（R1）
3003
3007
=σtype=laptop（Product）
=σtype=PC（Product）
=πmaker（R1）
=πmaker（R2）
=R3–R4
=ρPC1（PC）
R2:
=ρPC2（PC）
R3:
=R1
（PC1.hd=PC2.hdANDPC1.model<
>
PC2.model）R2
R4:
=πhd（R3）
hd
250
80
160
（PC1.speed=PC2.speedANDPC1.ram=PC2.ramANDPC1.model<
=πPC1.model,PC2.model（R3）
PC1.model
PC2.model
1012
=πmodel（σspeed≥2.80（PC））
πmodel（σspeed≥2.80（Laptop））
=πmaker,model（R1
Product）
=ρR3（maker2,model2）（R2）
=R2
（maker=maker2ANDmodel<
model2）R3
=πmaker（R4）
=πmodel,speed（PC）
=πmodel,speed（Laptop）
R2
=ρR4（model2,speed2）（R3）
=πmodel,speed（R3
（speed<
speed2）R4）
R6:
=R3–R5
=πmaker（R6
=πmaker,speed（Product
=ρR2（maker2,speed2）（R1）
=ρR3（maker3,speed3）（R1）
（maker=maker2ANDspeed<
speed2）R2
（maker3=makerANDspeed3<
speed2ANDspeed3<
speed）R3
=πmaker（R5）
D
=πmaker,model（Product
=ρR2（maker2,model2）（R1）
=ρR3（maker3,model3）（R1）
=ρR4（maker4,model4）（R1）
R5:
model2）R2
R6:
=R3
（maker3=makerANDmodel3<
model2ANDmodel3<
model）R5
R7:
（maker4=makerAND（model4=modelORmodel4=model2ORmodel4=model3））R6
R8:
=πmaker（R7）
=σbore≥16（Classes）
=πclass,country（R1）
class
country
Iowa
USA
NorthCarolina
Yamato
Japan
=σlaunched<
1921（Ships）
=πname（R1）
name
Haruna
Hiei
Kirishima
Kongo
Ramillies
Renown
Repulse
Resolution
Revenge
RoyalOak
RoyalSovereign
Tennessee
=σbattle=DenmarkStraitANDresult=sunk（Outcomes）
=πship（R1）
ship
Bismarck
Hood
=Classes
Ships
=σlaunched>
1921ANDdisplacement>
35000（R1）
=πname（R2）
Missouri
Musashi
NewJersey
Washington
Wisconsin
=σbattle=Guadalcanal（Outcomes）
=Ships
（ship=name）R1
=πname,displacement,numGuns（R3）
displacement
numGuns
32000
8
37000
9
=πname（Ships）
=πship（Outcomes）
=ρR3（name）（R2）
R3
California
Arizona
DukeofYork
Fuso
KingGeorgeV
PrinceofWales
Rodney
Scharnhorst
SouthDakota
WestVirginia
Yamashiro
From2.3.2,assumingthateveryclasshasoneshipnamedaftertheclass.
=πclass（Classes）
=πclass（σname<
class（Ships））
=R1–R2
=πcountry（σtype=bb（Classes））
=πcountry（σtype=bc（Classes））
=R1∩R2
Gt.Britain
=πship,result,date（Battles
（battle=name）Outcomes）
=ρR2（ship2,result2,date2）（R1）
（ship=ship2ANDresult=damagedANDdate<
date2）R2
=πship（R3）
Noresultsfromsampledata.
Exercise2.4.5
Theresultofthenaturaljoinhasonlyoneattributefromeachpairofequatedattributes.Ontheotherhand,theresultofthetheta-joinhasbothcolumnsoftheattributesandtheirvaluesareidentical.
Exercise2.4.6
Union
Ifweaddatupletotheargumentsoftheunionoperator,wewillgetallofthetuplesoftheoriginalresultandmaybetheaddedtuple.Iftheaddedtupleisaduplicatetuple,thenthesetbehaviorwilleliminatethattuple.Thustheunionoperatorismonotone.
Intersection
Ifweaddatupletotheargumentsoftheintersectionoperator,wewillgetallofthetuplesoftheoriginalresultandmaybetheaddedtuple.Iftheaddedtupledoesnotexistintherelationthatitisaddedbutdoesexistintheotherrelation,thentheresultsetwillincludetheaddedtuple.Thustheintersectionoperatorismonotone.
Difference
Ifweaddatupletotheargumentsofthedifferenceoperator,wemaynotgetallofthetuplesoftheoriginalresult.SupposewehaverelationsRandSandwearecomputingR–S.SupposealsothattupletisinRbutnotinS.TheresultofR–Swouldincludetuplet.However,ifweaddtuplettoS,thenthenewresultwillnothavetuplet.Thusthedifferenceoperatorisnotmonotone.
Projection
Ifweaddatupletotheargumentsoftheprojectionoperator,wewillgetallofthetuplesoftheoriginalresultandtheprojectionoftheaddedtuple.Theprojectionoperatoronlyselectscolumnsfromtherelationanddoesnotaffecttherowsthatareselected.Thustheprojectionoperatorismonotone.
Selection
Ifweaddatupletotheargumentsoftheselectionoperator,wewillgetallofthetuplesoftheoriginalresultandmaybetheaddedtuple.Iftheaddedtuplesatisfiestheselectcondition,thenitwillbeaddedtothenewresult.Theoriginaltuplesareincludedinthenewresultbecausetheystillsatisfytheselectcondition.Thustheselectionoperatorismonotone.
CartesianProduct
IfweaddatupletotheargumentsoftheCartesianproductoperator,wewillgetallofthetuplesoftheoriginalresultandpossiblyadditionaltuples.TheCartesianproductpairsthetuplesofonerelationwiththetuplesofanotherrelation.SupposethatwearecalculatingRxSwhereRhasmtuplesandShasntuples.IfweaddatupletoRthatisnotalreadyinR,thenweexpecttheresultofRxStohave（m+1）*ntuples.ThustheCartesianproductoperatorismonotone.
NaturalJoins
Ifweaddatupletotheargumentsofanaturaljoinoperator,wewillgetallofthetuplesoftheoriginalresultandpossiblyadditionaltuples.Thenewtuplecanonlycreateadditionalsuccessfuljoins,notless.If,however,the
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