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Access是一种桌面数据库,只适合数据量少的应用,在处理少量数据和单机访问的数据库时是很好的,效率也很高。但是它的同时访问客户端不能多于4个。access数据库有一定的极限,如果数据达到100M左右,很容易造成服务器iis假死,或者消耗掉服务器的内存导致服务器崩溃。ChrisPayne
September11,2000
Beforewegojumpingintocodeanddatabases,letstakeamomentandexaminetheneedsandstrategies,as
wellasthedifferenttypesofauctions.
Firstofall,therearemanydifferenttypesofauctions(whichwelldiscussinthenextsection),so
youllhavetodecidewhatyourneedsare,andadjustaccordingly.Illoutlinetheneedsforourauction
here,andwellreferencetheseasweprogress.First,letsgetsomedefinitionsoutoftheway:
Buyer/Bidder-Thepersonwhoplacesabid,andwantstobuyanitem.
Item/Lot-Onelistingintheauction(canbeseveralactualitems,butwillberepresentedbyone
listing).
Proxybidding-Abuyerplacesamaximumbidtoneverbeexceeded.Theactualbidthenissimplythelast
highestwinningbidplustheminimumincrement.Theactualbidwillbeincreasedautomaticallywhenoutbid
untilthemaxisreached.
Seller-Thepersonwholistedtheitemtobesold.
Winningbid-Thepriceabuyerpaystowinanitem.
Andnowourassumptions:
"SecondPriceauction:"Biddersmayplaceproxybids.Thewinnerswillthenenduppayingthelowest
winningbidfortheitem(s).
Wewillonlyallowsinglelotstobesold.Thismeanswewillnotallowgroupsoflotstobesoldtogether
(youwontbeabletosellitemsAandBtogether).However,youcansellabunchofitemsasonelot
(i.e.100pencilsinlotA).
Onceanauctionisover,itisover.Insomeauctions,ifabidisplacedwithinacertainamountoftime
(i.e.5seconds)beforetheendofanauction,theauctionisextendedforsometime.Wewillnotdothat
here.
Numberofitems.Inthecasethattwopeoplebidthesamething,thepersonwhobidformoreitemswill
win,regardlessofwhobidfirst.Ifbothbuyersbidforthesamenumberofitems,theearliestbidwill
win.
Proxybiddingrounds.Oneroundwillbedefinedaswhentheauctionenginecyclesthroughallusersand
adjustsbidsaccordingly,basedonthecurrenthighbidandthebuyersmaximumbid.Aroundwillcommence
onceabuyerplacesabidonalot,andwillproceedintheorderthebidswereplaced.Ifattheendof
theround,aresolutionisnotachieved,wewillstartoverfromthebeginning.
Therearealsotwoothertypesofauctionsthatwewillnotusehere,butmaybegoodforreference.
WinningBidAuction-Thewinningbuyergetstherequestedlotsforthepricetheybid.Ifthereare
multiplewinners,everyonegetsthepricetheybid.
ClearPriceAuction-Thewinningbuyersgettherequestedlotsforthelowestwinningbid.
Nowthatweveoutlinedourneeds,letstakealookatthedatabasestructurebehindtheauction.
ActiveServerPage技术为应用开发商提供了基于脚本的直观、快速、高效的应用开发手段,极大地提高了开发的效果。在讨论ASP的安全性问题之前,让我们来看看ASP是怎么工作的。 |
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