数据库整合版

1.DBMS:Adatabase-managementsystem(DBMS)isacollectionofinterrelateddataandasetofprogramstoaccessthosedata.2.Schema:Theoveralldesignofthedatabaseiscalledthedatabaseschema.3.Instance:Thecollectionofinformationstoredinthedatabaseataparticularmomentiscalledaninstanceofthedatabase.4.Datamodel:acollectionofconceptualtoolsfordescribingdata,datarelationships,datasemantics,andconsistencyconstraints.5.Domain:Foreachattribute,thereisasetofpermittedvalues,calledthedomainofthatattribute.6.DDL:Wespecifyadatabaseschemabyasetofdefinitionsexpressedbyaspeciallanguagecalledadata-definitionlanguage(DDL).7.DML:Adata-manipulationlanguage(DML)isalanguagethatenablesuserstoaccessormanipulatedataasorganizedbytheappropriatedatamodel.8.Entity:Anentityisa“thing”or“object”intherealworldthatisdistinguishablefromallotherobjects.9.Relationship:Arelationshipisanassociationamongseveralentities.10.Weakentityset:Anentitysetmaynothavesufficientattributestoformaprimarykey.Suchanentitysetistermedaweakentityset.11.1NF:WesaythatarelationschemaRisinfirstnormalform(1NF)ifthedomainofallattributesofRareatomic.12.Transactions:Atransactionisaunitofprogramexecutionthataccessesandpossiblyupdatesvariousdataitems.Collectionsofoperationsthatformsasinglelogicalunitofworkarecalledtransactions.13.SuperKey:Asuperkeyisasetofoneormoreattributesthat,takencollectively,allowustoidentifyuniquelyatupleintherelation.14.Candidatekey:Weareofteninterestedinsuperkeyforwhichnopropersubsetisasuperkey.Suchminimalsuperkeysarecalledcandidatekeys.15.Primarykey:Weusethetermprimarykeytodenoteacandidatekeythatischosenbythedatabasedesignerastheprincipalmeansofidentifyingtupleswithinarelation.16.Foreignkey:Arelationschema,sayr1,mayincludeamongitsattributestheprimarykeyofanotherrelationschema,sayr2.Thisattributesiscalledaforeignkeyfromr1,referencingr2.17.RAID:Avarietyofdisk-organizationtechniques,collectivelycalledredundantarraysofindependentdisks(RAID),havebeenproposedtoachieveimprovedperformanceandreliability.18.Clusteringindex:Ifthefilecontainingtherecordsissequentiallyordered,aclusteringindexisanindexwhosesearchkeyalsodefinesthesequentialorderofthefile.19.Denseindex:anindexrecordappearsforeverysearch-keyvalueinthefile.20.QueryOptimization:Queryoptimizationistheprocessofselectingthemostefficientquery-evaluationplanfromamongthemanystrategiesusuallypossibleforprocessingagivenquery,especiallyifthequeryiscomplex.21.Specialization:Theprocessofdesignatingsubgroupingswithinanentitysetiscalledspecialization.22.Schedule:Schedulesrepresentthechronologicalorderinwhichinstructionsareexecutedinthesystem.23.Conflictequivalent:IfascheduleScanbetransformedintoaschelueS’byaseriesofswapsofnon-conflictinginstructions,wesaythatSandS’areconflictequivalent.24.Conflictserializable:WesaythatascheduleSisconflictserializableifitisconflictequivalenttoaserialschedule.1.DBMS:Adatabase-managementsystemconsistsofacollectionofinterrelateddataandacollectionofprogramstoaccessthatdata.Thedatadesoribeoneparticularenterprise.数据库管理系统是有相关的数据和获取这些数据的程序集合组成的。这些数据描述了一个特定的实体。2.Databaseschema&DDL:Theoveralldesignifthedatabaseiscalledthedatabaseschema.Adatabaseschemaisspecifiedbyasetofdefinitionsthatareexpressedusingadata-definitionlanguage.数据库计划，数据库的全面计划称之为数据库计划。一个数据库计划是被定义的集合用数据定义语言所指定的。3.Datamodel:Underiyingthestructureofadatabaseisthedatamodelacollectionofconceptualtoolsfordesoroingdata,datareigtionships,datasemantics,anddataconstraints.数据模型，数据库潜在的结构模型叫做数据模型。十一系列数据概念性描述，数据关系，数据语义和数据约束。4.DML:adata-manipuiationlanguageisalanguagethatenablesuserstoaccessormanipuintedata.NonproceduralDMLs,whichrequireausertospeciryonlywhatdataareneeded,withoutspecifyingexaotiyhowtogetthosedata,arewidelyusedtoday数据库操作语言：数据库操作语言是使得用户可以获取或操作数据的一种语言。用户只要指定需要什么数据，并不需要精确的指定如何获取这些数据。DML现在非常广泛的应用。5.Entity:Anentityisanobjectthatexistsintherealworldandisdistinguishablefromotherobject.Weexpressthedistinctionbyassociatingwitheachentityasetofattributesthatdeseribestheobject.实体：实体是存在于显示世界中并且可以与其他事物区别开来的物体。我们用一系列的属性来描述这个实体以把它的差别描述出来。6.Reiationship:Arelationshipisanassociationamongseveralentites.关系：关系是几个实体之间的联系。7.Weakentityset&Srongentityset:Anentitysetthatdoesnothavesufficientattributestoformaprimarykeyistermedaweakentityset.Anentitysetthathasaprimarykeyistermedastrongentityset.弱实体集&强实体集：一个实体集如果没有足够的属性可以形成主键的称作弱实体集。有主键的实体集称作强实体集。8.Specialization:Specializationistheresultoftakingasubsetofahigher-levelentitysettoformalower-levelentityset.特殊化：特殊化是从高级的实体集拿出一个子集来形成低级实体形成的结果。9.QueryLanguages:Aquerylanguageislanguageisalanguageinwhichauserrequestsinformationfromthedatabase.查询语言：查询语言是用户在向数据库要求信息时使用的语言。10.Nonprocedurallanguage:theuserdescribesthedesiredinformationwithoutgivingaspecificprocedureforobtaininginformation.非过程化语言：用户在描述想要的信息时不用给出详细而精确的程序来获得信息。11.View:Anyrelationthatisthatisnotpartofthelogicalmodel,butismadevisibletoauserasavirtualrelation,iscalledaview.试图：试图不是逻辑模型的一部分，但是它对于一个虚拟关系的用户是可见的。12.1NF:WesaythatarelationschemaRisinfirstnormalformifthedomainsofallattributesofRareatomic.我们说如果一个关系策划所有属性的域都是原子的话我们称这个关系策划是第一范式。13．Atomic：Adomainisatomicifelementsofthedomain