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《數(shù)據(jù)庫系統(tǒng)原理》ppt課件-文庫吧

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【正文】 0。STAFF IDNAMEIDLASTNAME1Argentina1Jones2Canada2Smith3Cuba4Germany5FranceThestatementSELECT*FROMSTAFF,COUNTRYwillreturnhowmanyrows?A.2B.4C.5D.7E.10武漢大學(xué)國際軟件學(xué)院26問題 25:Giventhetabledefinition: CREATETABLEstudent(nameCHAR(30), ageINTEGER)Tolistthenamesofthe10youngeststudents,whichofthefollowingindexdefinitionstatementsonthestudenttablemayimprovethequeryperformance?A.CREATEINDEXyoungestONstudent(age,name)B.CREATEINDEXyoungestONstudent(name,age)C.CREATEINDEXyoungestONstudent(name,age DESC)D.CREATEINDEXyoungestONstudent(nameDESC) INCLUDE(age)武漢大學(xué)國際軟件學(xué)院27問題 26:Whyisauniqueindexnotsufficientforcreationofaprimarykey?A.Itissufficientaprimarykeyisthesamethingasauniqueindex.B.Uniqueindexescanbedefinedinascendingordescendingorder.Primarykeysmustbeascending.C.Auniqueindexcanbedefinedoveracolumnorcolumnsthatallownulls.Primarykeyscannotcontainnulls.D.Auniqueindexcanbedefinedoveracolumnorcolumnsthatallownulls.Thisisnotallowedforprimarykeysbecauseforeignkeyscannotcontainnulls.武漢大學(xué)國際軟件學(xué)院28問題 27:Whichtwoofthefollowingmodescanbeusedonthelocktablestatement?A.SHAREMODEB.EXCLUSIVEMODEC.REPEATABLEREADMODED.UNCOMMITTEDREADMODEE.INTENTEXCLUSIVEMODE武漢大學(xué)國際軟件學(xué)院29問題 28:Giventhefollowingcolumnrequirements:Col1NumericIdentifierFrom1to1000000Col2JobCodeVariable,1to2characterlongCol3JobDescriptionVariable,1to100characterslongCol4JobLengthLengthofJobinsecondsWhichofthefollowingwillminimizethediskspaceallocatetostoretherecordsifJobDescriptionhasaveragelengthof45?A.createtabletab1(col1int,col2char(2),col3char(100), col4int)B.createtabletab1(col1int,col2varchar(2),col3 char(100),col4int)C.createtabletab1(col1int,col2char(2),col3 varchar(100),col4int)D.createtabletab1(col1int,col2varchar(2),col3 varchar(100),col4int)武漢大學(xué)國際軟件學(xué)院30問題 29:Aviewisusedinsteadofatableforuserstodowhichofthefollowing?A.AvoidallocatingmorediskspaceperdatabaseB.ProvideuserswiththeabilitytodefineindexesC.Restrictuser’saccesstoasubsetofthetable dataD.Avoidallocatingfrequentlyusedqueryresulttables.武漢大學(xué)國際軟件學(xué)院31問題 30:Giventhefollowingtransaction: CREATETABLE(col1INT,col2INT) INSERTINTOVALUES(1,2) INSERTINTOVALUES(4,3) ROLLBACKWhichofthefollowingwouldbereturnedfromthestatementSELECT*FROM?A.COL1COL20record(s)selectedB.COL1COL2121record(s)selectedC.SQLCODE–204indicatingthat“”isanundefinednameD.COL1COL212416
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