外文文献—MySQL数据库Word文档下载推荐.docx

外文文献—MySQL数据库Word文档下载推荐.docx

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SimpleIntroduction

TheMySQLdatabasehasbecometheworld'

smostpopularopensourcedatabasebecauseofitshighperformance,highreliabilityandeaseofuse.ItisalsothedatabaseofchoiceforanewgenerationofapplicationsbuiltontheLAMPstackLinux,Apache,MySQL,PHP/Perl/Python.Manyoftheworld'

slargestandfastest-growingorganizationsincludingFacebook,Google,Adobe,AlcatelLucentandZapposrelyonMySQLtosavetimeandmoneypoweringtheirhigh-volumeWebsites,business-criticalsystemsandpackagedsoftware.

MySQLrunsonmorethan20platformsincludingLinux,Windows,MacOS,Solaris,IBMAIX,givingyouthekindofflexibilitythatputsyouincontrol.Whetheryou'

renewtodatabasetechnologyoranexperienceddeveloperorDBA,MySQLoffersacomprehensiverangeofdatabasetools,support,trainingandconsultingservicestomakeyousuccessful.

2.JavaandtheInternet

IfJavais,infact,yetanothercomputerprogramminglanguage,youmayquestionwhyitissoimportantandwhyitisbeingpromotedasarevolutionarystepincomputerprogramming.Theanswerisn’timmediatelyobviousifyou’recomingfromatraditionalprogrammingperspective.AlthoughJavaisveryusefulforsolvingtraditionalstand-aloneprogrammingproblems,itisalsoimportantbecauseitwillsolveprogrammingproblemsontheWorldWideWeb.

2.1Client-sideprogramming

TheWeb’sinitialserver-browserdesignprovidedforinteractivecontent,buttheinteractivitywascompletelyprovidedbytheserver.Theserverproducedstaticpagesfortheclientbrowser,whichwouldsimplyinterpretanddisplaythem.BasicHTMLcontainssimplemechanismsfordatagathering:

text-entryboxes,checkboxes,radioboxes,listsanddrop-downlists,aswellasabuttonthatcanonlybeprogrammedtoresetthedataontheformor“submit”thedataontheformbacktotheserver.ThissubmissionpassesthroughtheCommonGatewayInterfaceCGIprovidedonallWebservers.ThetextwithinthesubmissiontellsCGIwhattodowithit.Themostcommonactionistorunaprogramlocatedontheserverinadirectorythat’stypically

called“cgi-bin.”IfyouwatchtheaddresswindowatthetopofyourbrowserwhenyoupushabuttononaWebpage,youcansometimessee“cgi-bin”withinallthegobbledygookthere.Theseprogramscanbewritteninmostlanguages.Perlisacommonchoicebecauseitisdesignedfortextmanipulationandisinterpreted,soitcanbeinstalledonanyserverregardlessofprocessororoperatingsystem.

ManypowerfulWebsitestodayarebuiltstrictlyonCGI,andyoucaninfactdonearlyanythingwithit.However,WebsitesbuiltonCGIprogramscanrapidlybecomeoverlycomplicatedtomaintain,andthereisalsotheproblemofresponsetime.TheresponseofaCGIprogramdependsonhowmuchdatamustbesent,aswellastheloadonboththeserverandtheInternet.Ontopofthis,startingaCGIprogramtendstobeslow.TheinitialdesignersoftheWebdidnotforeseehowrapidlythisbandwidthwouldbeexhaustedforthekindsofapplicationspeopledeveloped.Forexample,anysortofdynamicgraphingisnearlyimpossibletoperformwithconsistencybecauseaGIFfilemustbecreatedandmovedfromtheservertotheclientforeachversionofthegraph.Andyou’venodoubthaddirectexperiencewithsomethingassimpleasvalidatingthedataonaninputform.Youpressthesubmitbuttononapage;

thedataisshippedbacktotheserver;

theserverstartsaCGIprogramthatdiscoversanerror,formatsanHTMLpageinformingyouoftheerror,andthensendsthepagebacktoyou;

youmustthenbackupapageandtryagain.Notonlyisthisslow,it’sinelegant.

Thesolutionisclient-sideprogramming.MostmachinesthatrunWebbrowsersarepowerful

enginescapableofdoingvastwork,andwiththeoriginalstaticHTMLapproachtheyaresittingthere,justidlywaitingfortheservertodishupthenextpage.Client-sideprogrammingmeansthattheWebbrowserisharnessedtodowhateverworkitcan,andtheresultfortheuserisamuchspeedierandmoreinteractiveexperienceatyourWebsite.

Theproblemwithdiscussionsofclient-sideprogrammingisthattheyaren’tverydifferentfromdiscussionsofprogrammingingeneral.Theparametersarealmostthesame,buttheplatformisdifferent:

aWebbrowserislikealimitedoperatingsystem.Intheend,youmuststillprogram,andthisaccountsforthedizzyingarrayofproblemsandsolutionsproducedbyclient-sideprogramming.Therestofthissectionprovidesanoverviewoftheissuesandapproachesinclient-sideprogramming.

2.2Plug-ins

Oneofthemostsignificantstepsforwardinclient-sideprogrammingisthedevelopmentoftheplug-in.Thisisawayforaprogrammertoaddnewfunctionalitytothebrowserbydownloadingapieceofcodethatplugsitselfintotheappropriatespotinthebrowser.Ittellsthebrowser“fromnowonyoucanperformthisnewactivity.”Youneedtodownloadtheplug-inonlyonce.Somefastandpowerfulbehaviorisaddedtobrowsersviaplug-ins,butwritingaplug-inisnotatrivialtask,andisn’tsomethingyou’dwanttodoaspartoftheprocessofbuildingaparticularsite.Thevalueoftheplug-inforclient-sideprogrammingisthatitallowsanexpertprogrammertodevelopanewlanguageandaddthatlanguagetoabrowserwithoutthepermissionofthebrowsermanufacturer.Thus,plug-insprovidea“backdoor”thatallowsthecreationofnewclient-sideprogramminglanguagesalthoughnotalllanguagesareimplementedasplug-ins.

2.3Scriptinglanguages

Plug-insresultedinanexplosionofscriptinglanguages.Withascriptinglanguageyouembedthesourcecodeforyourclient-sideprogramdirectlyintotheHTMLpage,andtheplug-inthatinterpretsthatlanguageisautomaticallyactivatedwhiletheHTMLpageisbeingdisplayed.Scriptinglanguagestendtobereasonablyeasytounderstandand,becausetheyaresimplytextthatispartofanHTMLpage,theyloadveryquicklyaspartofthesingleserverhitrequiredtoprocurethatpage.Thetrade-offisthatyourcodeisexposedforeveryonetoseeandsteal.Generally,however,youaren’tdoingamazinglysophisticatedthingswithscriptinglanguagessothisisnottoomuchofahardship.

ThispointsoutthatthescriptinglanguagesusedinsideWebbrowsersarereallyintendedtosolvespecifictypesofproblems,primarilythecreationofricherandmoreinteractivegraphicaluserinterfacesGUIs.However,ascriptinglanguagemightsolve80percentoftheproblemsencounteredinclient-sideprogramming.Yourproblemsmightverywellfitcompletelywithinthat80percent,andsincescriptinglanguagescanalloweasierandfasterdevelopment,youshouldprobablyconsiderascriptinglanguagebeforelookingatamoreinvolvedsolutionsuchasJavaorActiveXprogramming.

ThemostcommonlydiscussedbrowserscriptinglanguagesareJavaScriptwhichhasnothingtodowithJava;

it’snamedthatwayjusttograbsomeofJava’smarketingmomentum,VBScriptwhichlookslikeVisualBasic,andTcl/Tk,whichcomesfromthepopularcross-platformGUI-buildinglanguage.Thereareothersoutthere,andnodoubtmoreindevelopment.

JavaScriptisprobablythemostcommonlysupported.ItcomesbuiltintobothNetscapeNavigatorandtheMicrosoftInternetExplorerIE.Inaddition,thereareprobablymoreJavaScriptbooksavailablethantherearefortheotherbrowserlanguages,andsometoolsautomaticallycreatepagesusingJavaScript.However,ifyou’realreadyfluentinVisualBasicorTcl/Tk,you’llbemoreproductiveusingthosescriptinglanguagesratherthanlearninganewone.You’llhaveyourhandsfulldealingwiththeWebissuesalready.

2.4Java

Ifascriptinglanguagecansolve80percentoftheclient-sideprogrammingproblems,whatabouttheother20percent—the“reallyhardstuff?

”ThemostpopularsolutiontodayisJava.Notonlyisitapowerfulprogramminglanguagebuilttobesecure,cross-platform,andinternational,butJavaisbeingcontinuallyextendedtoprovidelanguagefeaturesandlibrariesthatelegantlyhandleproblemsthataredifficultintraditionalprogramminglanguages,suchasmultithreading,databaseaccess,networkprogramming,anddistributedcomputing.Javaallowsclient-sideprogrammingviatheapplet.

Anappletisamini-programthatwillrunonlyunderaWebbrowser.TheappletisdownloadedautomaticallyaspartofaWebpagejustas,forexample,agraphicisautomaticallydownloaded.Whentheappletisactivateditexecutesaprogram.Thisispartofitsbeauty—itprovidesyouwithawaytoautomaticallydistributetheclientsoftwarefromtheserveratthetimetheuserneedstheclientsoftware,andnosooner.Theusergetsthelatestversionoftheclientsoftwarewithoutfailandwithoutdifficultreinstallation.BecauseofthewayJavaisdesigned,theprogrammerneedstocreateonlyasingleprogram,andthatprogramautomaticallyworkswithallcomputersthathavebrowserswithbuilt-inJavainterpreters.Thissafelyincludesthevastmajorityofmachines.SinceJavaisafull-fledgedprogramminglanguage,youcandoasmuchworkaspossibleontheclientbeforeandaftermakingrequestsoftheserver.Forexample,youwon’tneedtosendarequestformacrosstheInternettodiscoverthatyou’vegottenadateorsomeotherparameterwrong,andyourclientcomputercanquicklydotheworkofplottingdatainsteadofwaitingfortheservertomakeaplotandshipagraphicimagebacktoyou.Notonlydoyougettheimmediatewinofspeedandresponsiveness,butthegeneralnetworktrafficandloadonserverscanbereduced,preventingtheentireInternetfromslowingdown.

OneadvantageaJavaapplethasovera