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1.ConfiguringApplicationCharacterSetandCollation RegardlessofhowyouconfiguretheMySQLcharactersetforapplicationuse,youmustalsoconsidertheenvironmentwithinwhichthoseapplicationsexecute.Forexample,ifyouintendtosendstatementsusingUTF-8texttakenfromafilethatyoucreateinaneditor,youshouldeditthefilewiththe...
1.概述 TheUnicodeStandardincludescharactersfromtheBasicMultilingualPlane(BMP)andsupplementarycharactersthatlieoutsidetheBMP.ThissectiondescribessupportforUnicodeinMySQL. BMPcharactershavethesecharacteristics: •Theircodepointvaluesarebetween0and65535(orU+0000andU+FFFF). •Theycanbeencodedinavariable-len...
MySQLincludescharacter【ˈkærəktər 字母，符号;】setsupportthatenablesyoutostoredatausingavariety【vəˈraɪəti(同一事物的)不同种类，多种式样;变化;(植物、语言等的)变种，变体;多样化;综艺节目;品种;多变性;异体;】ofcharactersetsandperformcomparisons【kəmˈpɛrəsənz比较;对比;相比;】accordingtoavarietyofcollations.ThedefaultMySQLservercharactersetandcollationareutf...
1.CharacterStringLiteral【ˈlɪtərəl字面意义的;缺乏想象力的;完全按原文的;】CharacterSetandCollation Everycharacterstringliteralhasacharactersetandacollation. ForthesimplestatementSELECT'string',thestringhastheconnectiondefaultcharactersetandcollationdefinedbythecharacter_set_connectionandcollation_connectionsystemvariab...
1.NUll值 TheNULLvaluecanbesurprisinguntilyougetusedtoit.Conceptually【kənˈsɛptʃuəli概念;观念上;概念上;在概念上;概念地;】,NULLmeans“amissingunknownvalue”anditistreatedsomewhatdifferentlyfromothervalues. TotestforNULL,usetheISNULLandISNOTNULLoperators,asshownhere: mysql>SELECT1ISNULL,1ISNOTNULL; +-----------+------...
1.age与出生日期 为什么设计的时候，存放的是出生日期而不是年龄呢？这个问题简单，细想很有意思，也包含着智慧，来自生产生活的思考。下面的解释很到位。 Howaboutage?Thatmightbeofinterest,butitisnotagoodthingtostoreinadatabase.Agechangesastimepasses,whichmeansyou'dhavetoupdateyourrecordsoften.Instead,itisbettertostoreafixedvaluesuchasdateofbirth.Then,wheneveryouneedage,youcan...
1. InnoDBINFORMATION_SCHEMAFULLTEXTIndexTables ThefollowingtablesprovidemetadataforFULLTEXTindexes: mysql>SHOWTABLESFROMINFORMATION_SCHEMALIKE'INNODB_FT%'; +-------------------------------------------+ |Tables_in_INFORMATION_SCHEMA(INNODB_FT%)| +-------------------------------------------+ ...
1.概述 Thissectionprovidesinformationandusage【ˈjuːsɪdʒ使用;(词语的)用法，惯用法;利用;利用率;】examplesforInnoDBINFORMATION_SCHEMAtables. InnoDBINFORMATION_SCHEMAtablesprovidemetadata,statusinformation,andstatisticsaboutvariousaspectsoftheInnoDBstorageengine.YoucanviewalistofInnoDBINFORMATION_SCHEMAtablesbyissuingaSHOW...
1.OnlineDDLSpaceRequirements DiskspacerequirementsforonlineDDLoperationsareoutlined【ˈaʊtlaɪnd概述;略述;显示…的轮廓;勾勒…的外形;】below.Therequirementsdonotapplytooperationsthatareperformedinstantly. •Temporarylogfiles: AtemporarylogfilerecordsconcurrentDMLwhenanonlineDDLoperationcreatesanindexoraltersatable.Thetem...
1.ForeignKeyOperations ThefollowingtableprovidesanoverviewofonlineDDLsupportforforeignkeyoperations.Anasterisk【ˈæstərɪsk星号(置于词语旁以引起注意或另有注释);】indicatesadditionalinformation,anexception,oradependency. Operation Instant InPlace RebuildsTable PermitsConcurrentDML OnlyModifiesMetadata Addingaforeign...
1.ColumnOperations ThefollowingtableprovidesanoverviewofonlineDDLsupportforcolumnoperations.Anasteriskindicatesadditionalinformation,anexception,oradependency. Operation Instant InPlace RebuildsTable PermitsConcurrentDML OnlyModifiesMetadata Addingacolumn Yes Yes No Yes Yes Droppingacolumn Ye...
1.概述 TheonlineDDLfeatureprovidessupportforinstantandin-placetablealterationsandconcurrentDML.Benefitsofthisfeatureinclude: •Improvedresponsiveness【rɪ'spɒnsɪvnəs响应性;灵敏度;敏感性;响应度;易起反应;】andavailability【əˌveɪlə'bɪləti可利用性;可利用；可用性；有用（效）性；使用价值；（有效）利用率；工作效率;】inbusyproductionenvironments,wheremakingatableuna...
1.概述 Therowformatofatabledetermineshowitsrowsarephysicallystored,whichinturncanaffecttheperformanceofqueriesandDMLoperations.Asmorerowsfitintoasinglediskpage,queriesandindexlookupscanworkfaster,lesscachememoryisrequiredinthebufferpool,andlessI/Oisrequiredtowriteoutupdatedvalues. Thedataineachtableis...
概述 ThissectionprovidesinformationabouttheInnoDBtablecompressionandInnoDBpagecompressionfeatures.Thepagecompressionfeatureisalsoreferredtoastransparentpagecompression. UsingthecompressionfeaturesofInnoDB,youcancreatetableswherethedataisstoredincompressedform.Compressioncanhelptoimprovebothrawperforma...
1MonitoringInnoDBTableCompressionatRuntime Overallapplicationperformance,CPUandI/Outilizationandthesizeofdiskfilesaregoodindicatorsofhoweffectivecompressionisforyourapplication.Thissectionbuildsontheperformancetuningadvice andshowshowtofindproblemsthatmightnotturnupduringinitialtesting. Todigde...
ConfiguringSpinLockPolling InnoDBmutexesandrw-locksaretypicallyreservedforshortintervals.Onamulti-coresystem,itcanbemoreefficientforathreadtocontinuously【kənˈtɪnjuəsli连续不断地】checkifitcanacquireamutexorrw-lockforaperiodoftimebeforeitsleeps.Ifthemutexorrw-lockbecomesavailableduringthisperiod,thethreadc...
概述 Thissectiondescribeshowtoconfigurepersistentandnon-persistentoptimizerstatisticsforInnoDBtables. Persistentoptimizerstatisticsarepersistedacrossserverrestarts【意思是重启操作，对这些数据没有影响】,allowingforgreaterplanstabilityandmoreconsistentqueryperformance.Persistentoptimizerstatisticsalsoprovidecontrolandflex...
1.ConfiguringNon-PersistentOptimizerStatisticsParameters 开始讲解非固化的统计数据 Thissectiondescribeshowtoconfigurenon-persistentoptimizerstatistics.Optimizerstatisticsarenotpersistedtodiskwheninnodb_stats_persistent=OFForwhenindividualtablesarecreatedoralteredwithSTATS_PERSISTENT=0.Instead,statisticsarestored...
1.SavingandRestoringtheBufferPoolState 主要内容为【热启动】，就是把之前常用的内存数据，按照划定的比例快速重新加载到内存中。 Toreducethewarmupperiodafterrestartingtheserver,InnoDBsavesapercentageofthemostrecentlyusedpagesforeachbufferpoolatservershutdownandrestoresthesepagesatserverstartup.Thepercentageofrecentlyusedpagesthatisstoredisdefine...
1.ConfiguringThreadConcurrencyforInnoDB InnoDBusesoperatingsystemthreadstoprocessrequestsfromusertransactions.(TransactionsmayissuemanyrequeststoInnoDBbeforetheycommitorrollback.)Onmodernoperatingsystemsandserverswithmulti-coreprocessors,wherecontextswitchingisefficient,mostworkloadsrunwellwithoutan...