【正文】 將介紹著名數(shù)據(jù)庫語言的SQL的基本形式。SQL是允許我們查詢和操作關(guān)于計(jì)算機(jī)化的關(guān)系數(shù)據(jù)庫系統(tǒng)的語言。從80 年代初期，SQL就一直是關(guān)系數(shù)據(jù)庫管理系統(tǒng)的語言，而且它是有著重要的意義的在對(duì)許多概念中，都在本文里提到。當(dāng)前，SQL語言是從關(guān)系形式(ANSI SQL 92 標(biāo)準(zhǔn)) 轉(zhuǎn)向一個(gè)新的對(duì)象關(guān)系形式(ANSI SLQ 99，1999 被發(fā)布)。SQL99 是SQL92的延伸，它不改變所有早期版本的優(yōu)秀的語言。通常，我們嚴(yán)格定義的基本SQL與ANSI SQL 標(biāo)準(zhǔn)和基礎(chǔ)子集十分類似，分別被認(rèn)為就是ENTRY SQL92 和CORE SQL99。我們也介紹了ENTRY SQL9CORE SQL99之外一些廣泛實(shí)現(xiàn)的特性。在定義基本的SQL中，我們的試金石是將提供一種支持大多RDBMS 接口的語法。首先，我們總的研究SQL的特性，然后對(duì)SQL的多種形式標(biāo)準(zhǔn)和產(chǎn)品語言以及我們將如何具體地處理這些標(biāo)準(zhǔn)和產(chǎn)品語言進(jìn)行分析解釋。我們知道了怎樣完成關(guān)系代數(shù)來回應(yīng)對(duì)查詢的數(shù)據(jù)庫信息。這將讓我們看到，在編寫查詢語句時(shí)SQL中的SELECT在很多方面都比關(guān)系代數(shù)強(qiáng)大。但是，二者在性能上相比較，SQL在本質(zhì)上并沒有明顯的改進(jìn)。對(duì)那些周密的擴(kuò)展語法來說，沒有關(guān)系代數(shù)所不能實(shí)現(xiàn)的。所以，關(guān)系代數(shù)查詢方面的經(jīng)驗(yàn)就能成為SQL查詢的很好的借鑒。同時(shí)在許多方面，SQL語句和關(guān)系代數(shù)概念模型又有著相當(dāng)大的差異，而可以通過熟悉、理解關(guān)系代數(shù)增強(qiáng)對(duì)SQL的理解。最重要的SQL特性是它擁有在計(jì)算機(jī)輸出的條件下能夠相互地構(gòu)造查詢的能力。SQL的SELECT語句比簡(jiǎn)單的關(guān)系代數(shù)更難，但只要能夠上機(jī)實(shí)踐，只需幾個(gè)典型實(shí)驗(yàn)就收回你的懷疑。我們所談?wù)摰慕换ナ江h(huán)境是你在電腦上一輸入一個(gè)查詢語句并且立即執(zhí)行，就可以看到結(jié)果。此情況說明了這樣一個(gè)事實(shí)，一個(gè)SQL 的SELECT語句是在打入一些輸入行之后立即形成的，并且對(duì)一個(gè)用戶來說該語句與前面的任何交互操作都沒有關(guān)系。這種不依賴于用戶會(huì)話互相通信操作的性質(zhì)也被稱作非過程性。在這方面SQL也與關(guān)系代數(shù)不同，因?yàn)樵陉P(guān)系代數(shù)中為了表示一個(gè)表與自身的笛卡兒積，在表前面可能需要定義表別名。SQL與比如JAVA或C之類的語言之間的差別十分巨大的：你不需要為了實(shí)現(xiàn)一個(gè)SQL查詢的功能而編寫一個(gè)程序，你只需要量輸入較短的、獨(dú)立的查詢語句，然后運(yùn)行就可以了。當(dāng)然，SQL查詢可能會(huì)復(fù)雜。為此，我們列出了SELECT語句的完整形式。取出這個(gè)形式的一個(gè)部分的查詢被稱為子查詢，對(duì)它的定義是遞歸的，完整的SELECT語句形式只有一個(gè)子句。無論如何，你不應(yīng)恐懼復(fù)雜的SQL語句。SELECT語句的非過程性說明了它與使用菜單的應(yīng)用十分相似。在使用菜單的應(yīng)用中，用戶需要從菜單中填寫一組數(shù)據(jù)，然后按下回車來對(duì)它們立即執(zhí)行。SELECT語句的各種子句對(duì)于菜單選項(xiàng)有時(shí)也會(huì)需要所有的子句，但并不是所有的子句在每次查詢的時(shí)候都用上。觀察可靠性應(yīng)考慮系統(tǒng)使用環(huán)境。依照已經(jīng)討論的內(nèi)容，系統(tǒng)環(huán)境無法預(yù)先被描述，系統(tǒng)設(shè)計(jì)者也不可能對(duì)系統(tǒng)工作環(huán)境做過多限制。不同的系統(tǒng)對(duì)相同環(huán)境中的同樣問題還可能有無法預(yù)料的反應(yīng)，所有這些都影響系統(tǒng)的可靠性。因此，即使在系統(tǒng)被集成之后，它的可靠性也是難以精確測(cè)量的。7 Visual Basic訪問數(shù)據(jù)庫的前景近來隨著Web應(yīng)用軟件的迅速發(fā)展和現(xiàn)有數(shù)據(jù)存儲(chǔ)形式的多種多樣，Visual Basic訪問數(shù)據(jù)庫的解決方案面臨諸如快速提取分布于企業(yè)內(nèi)部和外部有用商業(yè)信息等的多種挑戰(zhàn)。為此Microsoft提出一種新的數(shù)據(jù)庫訪問策略，即“統(tǒng)一數(shù)據(jù)訪問”（UniversalDataAccess）的策略?！敖y(tǒng)一數(shù)據(jù)訪問”提供了高性能的存取包括關(guān)系型和非關(guān)系型在內(nèi)的多種數(shù)據(jù)源，提供獨(dú)立于開發(fā)工具和開發(fā)語言的簡(jiǎn)單的編程接口，這些技術(shù)使得企業(yè)集成多種數(shù)據(jù)源、選擇更好的開發(fā)工具、應(yīng)用軟件、操作平臺(tái)、建立容易維護(hù)的解決方案成為可能。附錄B 外文原文The Active Server PagesThe Active Server Pages( ASP) is a server to carry the script plait writes the environment, using it can create to set up with circulate the development, alternant Web server application procedure. Using the ASP cans bine the page of HTML, script order to create to set up the alternant the page of Web with the module of ActiveX with the mighty and applied procedure in function that according to Web. The applied procedure in ASP develops very easily with modify.1 The working principle of ASP When the Web site into the ASP feature, will take place the following things: （1）the user browser address bar to enter a URL, the default page of the expansion are. Asp. （2）the browser request to the server. （3）the server engine running ASP procedures. （4）ASP document in accordance with the order from top to bottom starting with the implementation of the script orders, the implementation of HTML page content. （5）pages of information sent to the browser. 2 ASP operating environment Asp need to run in under the PWS or IIS. PWS or IIS services in windows98 or windows2000 on the fringe of the CDROM, can use the Add / Remove Programs in the Add / Remove windows ponents to install. Asp and the general need to access databases or a bination of SQL Server database, made a powerful process. ASP can run the web server software Windows2000 default installation is (internet information server), and the default installation of windows xp is , windows 2003 default installation of . PWS (personal web server) running windows98 environment in a simple personal Web server. 3 ASP and the meaning of ASP (Application Service Provider, application software rental service providers) refers through the Internet to provide application software rental services industry, refers to the application software industry as the mainstay, and through onetomany network Transmission services, such servicebased business transactions to be leased by the way, in a more costeffective manner has the right to use the software, and also because the industry centralized management and greatly reduce the cost of maintaining enterprises . Basically, ASP is a software services, Internet services, and outsourcing of information services and network integration and access of products, access products, such as the three major characteristics, can even be seen as ISP ( Internet Service Provider) and ITS (Information Technology Service) bination. ASP is the English Application Service Provider, the standard Chinese translation is application service provider, is defined as mercial or individual customer management applications to provide solutions for panies or enterprises. ASP Chaozuo recently by the media is very fiery, the IT industry is not facing a pile of technical terms it is very difficult to clarify terminology ASP content, the paper tried to use simple language to the broad masses of readers opened the mysterious veil of ASP, IT Top of the ASP industry areas have some basic knowledge. 4 Origin of ASP The research to ASP mode and ASP enterprise39。s origin can proceed with two respects , one to in terms of business and technology , is it carry on research to e from ASP developing history that business mit。 Another one is studies the origins of ASP enterprises and evolution course at present in terms of organization39。s development.Whether stand up synthetically abovementioned developing stage, to put it briefly, present ASP history and development path of provider can simple to describe as:The first, developed from the past ISP, rounded the infrastructure and munication function, cooperate with software manufacturer, increase the business scope, develop into the present IDC (the data centre of Internet)；The second，the past ISV (independent software provider ) and VAR (the trader that resells valueadded service ), at Internet age , changed the marketing way in the past , would rely mainly on sale of the software product to change direction to rely mainly on the fact that right to use is leased in the past, bale from physics carrier encapsulation way change direction and longrange operation way main fact now, through the cooperation with network operator , realize the transition to ASP；The third ，IT service departments and t