11Multi-RangeReadOptimization Readingrowsusingarangescanonasecondaryindexcanresultinmanyrandomdiskaccessestothebasetablewhenthetableislargeandnotstoredinthestorageengine'scache.WiththeDisk-SweepMulti-RangeRead(MRR)optimization,MySQLtriestoreducethenumberofrandomdiskaccessforrangescansbyfirstscanning...

15ISNULLOptimization MySQLcanperformthesameoptimizationoncol_nameISNULLthatitcanuseforcol_name=constant_value.Forexample,MySQLcanuseindexesandrangestosearchforNULLwithISNULL. Examples: SELECTFROMtbl_nameWHEREkey_colISNULL; SELECTFROMtbl_nameWHEREkey_col<=>NULL; SELECTFROMtbl_name WHEREkey_col...

RockyLinux官方宣布，RockyLinux9.0操作系统全面上市，可作为CentOSLinux和CentOSStream的直接替代品。有些安装需要测试验证的。 1.下载的安装包  2.安装的过程 此安装包,RockyLinux环境下安装,与在centos7.9下安装是一样的。 不再赘述. 3.通过MySQL客户端连接 MySQL服务正常,进程也正常,但是通过MySQL客户端连接报错。 连接命令 mysql-u用户名-p 报错的msg mysql:errorwhileloadingsharedlibraries:libtinfo.so.5:cannotopenshare...

1.Seconds_Behind_Source TheSHOWREPLICASTATUSstatement,whichyoumustexecuteoneachreplica,providesinformationabouttheconfigurationandstatusoftheconnectionbetweenthereplicaserverandthesourceserver.FromMySQL8.0.22,SHOWSLAVESTATUSisdeprecated,andSHOWREPLICASTATUSisavailabletouseinstead.ThePerformanceSchem...

1. Replication  for purposes--UsingReplicationforBackups Replicationcanbeusedinmanydifferentenvironmentsforarangeofpurposes. Tousereplicationasabackupsolution,replicatedatafromthesourcetoareplica,andthenbackupthereplica.Thereplicacanbepausedandshutdownwithoutaffectingtherunningop...

Inadditiontothebuilt-inasynchronousreplication,MySQL8.0supportsaninterfacetosemisynchronousreplicationthatisimplementedbyplugins.Thissectiondiscusseswhatsemisynchronousreplicationisandhowitworks.Thefollowingsectionscovertheadministrativeinterfacetosemisynchronousreplicationandhowtoinstall,configure,...

1.DelayedReplication MySQLsupportsdelayedreplicationsuchthatareplicaserverdeliberately【dɪˈlɪbərətli故意;蓄意;存心;从容不迫地;不慌不忙地;小心翼翼地;】executestransactionslaterthanthesourcebyatleastaspecified【ˈspesɪfaɪd明确规定;具体说明;详述;详列;】amountoftime.  InMySQL8.0,themethodofdelayingreplicationdependsontwotimestamps,imme...

Optimizationinvolves【ɪnˈvɑːlvz需要;影响;(使)参加，加入;包含;牵涉;牵连;使成为必然部分(或结果);】configuring,tuning,andmeasuringperformance,atseverallevels.Dependingonyourjobrole(developer,DBA,oracombinationofboth),youmightoptimizeatthelevelofindividual【ˌɪndɪˈvɪdʒuəl单独的;个别的;独特的;一个人的;与众不同的;】SQLstatements,entireapplications,asing...

Queries,intheformofSELECTstatements,performallthelookupoperationsinthedatabase.Tuningthesestatementsisatoppriority,whethertoachievesub-secondresponsetimesfordynamicwebpages,ortochophoursoffthetimetogeneratehugeovernightreports. BesidesSELECTstatements,thetuningtechniquesforqueriesalsoapplytoconstruc...

3.IndexMergeOptimization TheIndexMergeaccessmethodretrievesrowswithmultiplerangescansandmerges【ˈmɜːrdʒɪz(使)合并，结合，并入;融入;相融;渐渐消失在某物中;】theirresultsintoone.Thisaccessmethodmergesindexscansfromasingletableonly,notscansacrossmultipletables.Themergecanproduceunions,intersections,orunions-of-intersectionsof...

8.NestedJoinOptimization Thesyntaxforexpressingjoinspermitsnestedjoins. Thesyntaxoftable_factorisextendedincomparisonwiththeSQLStandard.Thelatteracceptsonlytable_reference,notalistoftheminsideapairofparentheses.Thisisaconservative【kənˈsɜːrvətɪv保守的;(英国)保守党的;守旧的;低于实际数量的;】extensionifweconsidereachcomma...

1. Thefollowingoptionsalsohaveanimpactonthesource: •ForthegreatestpossibledurabilityandconsistencyinareplicationsetupusingInnoDBwithtransactions,youshoulduse innodb_flush_log_at_trx_commit=1andsync_binlog=1inthesource'smy.cnffile. •Ensurethattheskip_networkingsystemvariableisnotenabledonthesour...

1. ...行业的数字化转型也进入了深水期，我们看到技术与场景的深度融合所带来的创新体验，看到了数字化加持下的流程再造和效率提升，也看到了行业引领者在业务模式和商业模式创新方面孜孜不倦的探索。 ...数字经济蓬勃发展时代，数据已成为关键生产要素。数据赋能企业经营决策、业务模式创新的需求不断变化，已经新兴技术工具的有效支撑，推动数据向数据要素化、数据驱动化阶段跃迁，实现数据价值崛起。 ...数字化在赋能行业对抗风险、增加韧性的同时，也将能够更好地助力其在未来朝着更加多元化、个性化和高质量的方向发展。 2. 在探索新模式的过程当中，定位和心态的转变，是保障其整个数字化转型成功的重要软性条件。其中有...

Alockingread,anUPDATE,oraDELETEgenerallysetrecordlocksoneveryindexrecordthatisscannedintheprocessingofanSQLstatement.ItdoesnotmatterwhetherthereareWHEREconditionsinthestatementthatwouldexcludetherow.InnoDBdoesnotremembertheexact【ɪɡˈzækt准确的;精确的;严格的;精密的;严谨的;严密的;一丝不苟的;】WHEREcondition,butonlyknowswhichi...

Toimplementalarge-scale,busy,orhighlyreliabledatabaseapplication,toportsubstantial【səbˈstænʃl】codefromadifferentdatabasesystem,ortotuneMySQLperformance,itisimportanttounderstandInnoDBlockingandtheInnoDBtransactionmodel. 1.SharedandExclusiveLocks InnoDBimplements【ˈɪmplɪments实施;执行;贯彻;使生效;】standardrow-...

TheInnoDBtransactionmodelaimstocombinethebestproperties【ˈprɑpərtiz财产;特性;房地产;不动产;财物;庄园;所有物;房屋及院落;】ofamulti-versioningdatabasewithtraditionaltwo-phaselocking.InnoDBperformslockingattherowlevelandrunsqueriesasnonlockingconsistentreadsbydefault,inthestyleofOracle.ThelockinformationinInnoDBisstoredspace-...

1.DataTypeDefaultValues Datatypespecificationscanhaveexplicit【ɪkˈsplɪsɪt明确的;详述的;直言的,坦率的;一目了然的;】orimplicit【ɪmˈplɪsɪt含蓄的;完全的;内含的;无疑问的;不直接言明的;成为一部分的;】defaultvalues. ADEFAULTvalueclauseinadatatypespecificationexplicitlyindicatesadefaultvalueforacolumn.Examples: CREATETABLEt1( iINTDEFAULT-1, cVARCHAR(10...

ThestringdatatypesareCHAR,VARCHAR,BINARY,VARBINARY,BLOB,TEXT,ENUM,andSET. 1.StringDataTypeSyntax Insomecases,MySQLmaychangeastringcolumntoatypedifferentfromthatgiveninaCREATETABLEorALTERTABLEstatement.  Fordefinitionsofcharacterstringcolumns(CHAR,VARCHAR,andtheTEXTtypes),MySQLinterprets【ɪnˈtɜːr...

前述 Datatypedescriptionsusetheseconventions: •Forintegertypes,Mindicatesthemaximumdisplaywidth.Forfloating-pointandfixed-pointtypes,Misthetotalnumberofdigitsthatcanbestored(theprecision).Forstringtypes,Misthemaximumlength.ThemaximumpermissiblevalueofMdependsonthedatatype. •Dappliestofloating-pointand...

1.SupportedCharacterSetsandCollations Tolisttheavailablecharactersetsandtheirdefaultcollations,usetheSHOWCHARACTERSETstatementorquerytheINFORMATION_SCHEMACHARACTER_SETStable. mysql>SHOWCHARACTERSET; Incaseswhereacharactersethasmultiplecollations,itmightnotbeclearwhichcollationismostsuitablefora...