数据库系统概念全套配套课件PPT appC.ppt

《数据库系统概念全套配套课件PPT appC.ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、AppendixC:OtherRelationalLanguagesAppendixC:OtherRelationalLanguagesQuery-by-Example(QBE)AccessDatalogQuery-by-Example(QBE)BasicStructureQueriesonOneRelationQueriesonSeveralRelationsTheConditionBoxTheResultRelationOrderingtheDisplayofTuplesAggregateOperationsModificationoftheDatabaseQBE—BasicStructu

2、reAgraphicalquerylanguagewhichisbased(roughly)onthedomainrelationalcalculusTwodimensionalsyntax–systemcreatestemplatesofrelationsthatarerequestedbyusersQueriesareexpressed“byexample”QBESkeletonTablesfortheBankExampleQBESkeletonTables(Cont.)QueriesonOneRelationFindallloannumbersatthePerryridgebranch.

3、_xisavariable(optional;canbeomittedinabovequery)P.meansprint(display)duplicatesareremovedbydefaultToretainduplicatesuseP.ALLP._xQueriesonOneRelation(Cont.)DisplayfulldetailsofallloansP._xP._yP._zMethod1:Method2:ShorthandnotationQueriesonOneRelation(Cont.)FindnamesofallbranchesthatarenotlocatedinBroo

4、klynFindtheloannumberofallloanswithaloanamountofmorethan$700QueriesonOneRelation(Cont.)FindtheloannumbersofallloansmadejointlytoSmithandJones.FindallcustomerswholiveinthesamecityasJones.QueriesonSeveralRelationsFindthenamesofallcustomerswhohavealoanfromthePerryridgebranch.QueriesonSeveralRelations(C

5、ont.)Findthenamesofallcustomerswhohavebothanaccountandaloanatthebank.NegationinQBEFindthenamesofallcustomerswhohaveanaccountatthebank,butdonothavealoanfromthebank.¬means“theredoesnotexist”NegationinQBE(Cont.)Findallcustomerswhohaveatleasttwoaccounts.¬means“notequalto”TheConditionBoxAllowstheexpressi

6、onofconstraintsondomainvariablesthatareeitherinconvenientorimpossibletoexpresswithintheskeletontables.ComplexconditionscanbeusedinconditionboxesExample:FindtheloannumbersofallloansmadetoSmith,toJones,ortobothjointlyConditionBox(Cont.)QBEsupportsaninterestingsyntaxforexpressingalternativevalues.Condi

7、tionBox(Cont.)Findallaccountnumberswithabalancegreaterthan$1,300andlessthan$1,500.Findallaccountnumberswithabalancegreaterthan$1,300andlessthan$2,000butnotexactly$1,500.ConditionBox(Cont.)Findallbranc