数据库系统基础教程第二章答案

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2、 modelspeedmaker,modelmodelspeedR3(maker2,model2)(maker = maker2 AND model model2)makerBEmodel,speedmodel,speedR4(model2,speed2)model,speed(speed speed2 )makerB maker,speedR2(maker2,speed2)R3(maker3,speed3)maker(maker = maker2 AND speed speed2)(maker3 = maker AND speed3 speed2 AND speed3 speed)ADE m

3、aker,modelR2(maker2,model2)R3(maker3,model3)R4(maker4,model4)(maker = maker2 AND model model2)(maker3 = maker AND model3 model2 AND model3 model)(maker4 = maker AND (model4=model OR model4=model2 OR model4=model3)makerABDEmakermodelspeed3.00hd 100model,pricemodel,pricemodel,pricemaker=Bmaker=Bmaker=

4、BPrinterProductLaptopProductProductmodelmakermakercolor = true AND type = lasertype=PCtype=laptophd(PC1.hd = PC2.hd AND PC1.model PC2.model)PC2PC1PC1.model,PC2.model(PC1.speed = PC2.speed AND PC1.ram = PC2.ram AND PC1.model PC2.model)PC2PC1maker(maker = maker2 AND model model2)R3(maker2,model2)maker

5、,modelProductmodelmodelspeed 2.80speed2.80PCLaptopmakerProductmodel,speed(speed speed2 )R4(model2,speed2)model,speedmodel,speedPCLaptopmaker(maker3 = maker AND speed3 speed2 AND speed3 speed)(maker = maker2 AND speed speed2)R2(maker2,speed2)R3(maker3,speed3)maker,speedProductPCmaker(maker4 = maker A

6、ND (model4=model OR model4=model2 OR model4=model3)(maker3 = maker AND model3 model2 AND model3 model)(maker = maker2 AND model model2)R2(maker2,model2)R3(maker3,model3)R4(maker4,model4)maker,modelProductPCbore16class,country launched1921ANDdisplacement35000name battle=Guadalcanal(ship=name)name,dis

7、placement,numGuns89 name shipR3(name) V name countrytype=bbcountrytype=bc ship,result,dateR2(ship2,result2,date2)(battle=name)(ship=ship2 AND result=damaged AND date date2)ship class,countryshipnamebore 16launched 1921 AND displacement 35000(ship=name)battle=GuadalcanalR3(name)nameclassclassshipname

8、 classship(ship=ship2 AND result=damaged AND date date2)R2(ship2,result2,date2)countrycountryship,result,datetype=bbtype=bc(battle=name)BattlesOutcomes a a a a RS R tR RS. t tuple. a a a RxSRmSn aR RxSm+ *n a a a a a a a a a RS hasn+m m,) n*m C n*m C L theresulting S is.L L (R) nm,L r Rs rR rsR r r R R- Anr = ANDhd AND 16 = 9ANDbore = a class,name R2(class2,name2)R3(class3,name3)(class = class2 AND name name2) (class=class3 AND name name3 AND name2 name3)= =bb countrytype= = a ship,battle,result,class ship,batt