數(shù)據(jù)庫(kù) 外文翻譯

1、A introduction to Database Management SystemRaghu RamakrishnanA database (sometimes spelled data base) is also called an electronic database , referring to any collection of data, or information, that is specially organized for rapid search and retrieval by a computer. Databases are structured to fa

2、cilitate the storage, retrieval , modification, and deletion of data in conjunction with various data-processing operations .Databases can be stored on magnetic disk or tape, optical disk, or some other secondary storage device.A database consists of a file or a set of files. The information in thes

3、e files may be broken down into records, each of which consists of one or more fields. Fields are the basic units of data storage , and each field typically contains information pertaining to one aspect or attribute of the entity described by the database . Using keywords and various sorting command

4、s, users can rapidly search , rearrange, group, and select the fields in many records to retrieve or create reports on particular aggregate of data.Complex data relationships and linkages may be found in all but the simplest databases .The system software package that handles the difficult tasks ass

5、ociated with creating ,accessing, and maintaining database records is called a database management system(DBMS).The programs in a DBMS package establish an interface between the database itself and the users of the database. (These users may be applications programmers, managers and others with info

6、rmation needs, and various OS programs.)A DBMS can organize, process, and present selected data elements form the database. This capability enables decision makers to search, probe, and query database contents in order to extract answers to nonrecurring and unplanned questions that arent available i

7、n regular reports. These questions might initially be vague and/or poorly defined ,but people can “browse” through the database until they have the needed information. In short, the DBMS will “manage” the stored data items and assemble the needed items from the common database in response to the que

8、ries of those who arent programmers.A database management system (DBMS) is composed of three major parts:(1)a storage subsystem that stores and retrieves data in files;(2) a modeling and manipulation subsystem that provides the means with which to organize the data and to add , delete, maintain, and

9、 update the data;(3)and an interface between the DBMS and its users. Several major trends are emerging that enhance the value and usefulness of database management systems;Managers: who require more up-to-data information to make effective decisionCustomers: who demand increasingly sophisticated inf

10、ormation services and more current information about the status of their orders, invoices, and accounts.Users: who find that they can develop custom applications with database systems in a fraction of the time it takes to use traditional programming languages.Organizations : that discover informatio

11、n has a strategic value; they utilize their database systems to gain an edge over their competitors.The Database ModelA data model describes a way to structure and manipulate the data in a database. The structural part of the model specifies how data should be represented(such as tree, tables, and s

12、o on ).The manipulative part of the model specifies the operation with which to add, delete, display, maintain, print, search, select, sort and update the data.Hierarchical Model The first database management systems used a hierarchical model-that is-they arranged records into a tree structure. Some

13、 records are root records and all others have unique parent records. The structure of the tree is designed to reflect the order in which the data will be used that is ,the record at the root of a tree will be accessed first, then records one level below the root ,and so on.The hierarchical model was

14、 developed because hierarchical relationships are commonly found in business applications. As you have known, an organization char often describes a hierarchical relationship: top management is at the highest level, middle management at lower levels, and operational employees at the lowest levels. N

15、ote that within a strict hierarchy, each level of management may have many employees or levels of employees beneath it, but each employee has only one manager. Hierarchical data are characterized by this one-to-many relationship among data.In the hierarchical approach, each relationship must be expl

16、icitly defined when the database is created. Each record in a hierarchical database can contain only one key field and only one relationship is allowed between any two fields. This can create a problem because data do not always conform to such a strict hierarchy.Relational Model A major breakthroug

17、h in database research occurred in 1970 when E. F. Codd proposed a fundamentally different approach to database management called relational model ,which uses a table as its data structure.The relational database is the most widely used database structure. Data is organized into related tables. Each

18、 table is made up of rows called and columns called fields. Each record contains fields of data about some specific item. For example, in a table containing information on employees, a record would contain fields of data such as a persons last name ,first name ,and street address.Structured query la

19、nguage(SQL)is a query language for manipulating data in a relational database .It is nonprocedural or declarative, in which the user need only specify an English-like description that specifies the operation and the described record or combination of records. A query optimizer translates the descrip

20、tion into a procedure to perform the database manipulation.Network ModelThe network model creates relationships among data through a linked-list structure in which subordinate records can be linked to more than one parent record. This approach combines records with links, which are called pointers.

21、The pointers are addresses that indicate the location of a record. With the network approach, a subordinate record can be linked to a key record and at the same time itself be a key record linked to other sets of subordinate records. The network mode historically has had a performance advantage over

22、 other database models. Today , such performance characteristics are only important in high-volume ,high-speed transaction processing such as automatic teller machine networks or airline reservation system.Both hierarchical and network databases are application specific. If a new application is deve

23、loped ,maintaining the consistency of databases in different applications can be very difficult. For example, suppose a new pension application is developed .The data are the same, but a new database must be created.Object Model The newest approach to database management uses an object model , in wh

24、ich records are represented by entities called objects that can both store data and provide methods or procedures to perform specific tasks.The query language used for the object model is the same object-oriented programming language used to develop the database application .This can create problems

25、 because there is no simple , uniform query language such as SQL . The object model is relatively new, and only a few examples of object-oriented database exist. It has attracted attention because developers who choose an object-oriented programming language want a database based on an object-orient

26、ed model.Distributed DatabaseSimilarly , a distributed database is one in which different parts of the database reside on physically separated computers . One goal of distributed databases is the access of information without regard to where the data might be stored. Keeping in mind that once the us

27、ers and their data are separated , the communication and networking concepts come into play .Distributed databases require software that resides partially in the larger computer. This software bridges the gap between personal and large computers and resolves the problems of incompatible data formats

28、. Ideally, it would make the mainframe databases appear to be large libraries of information, with most of the processing accomplished on the personal computer.A drawback to some distributed systems is that they are often based on what is called a mainframe-entire model , in which the larger host co

29、mputer is seen as the master and the terminal or personal computer is seen as a slave. There are some advantages to this approach . With databases under centralized control , many of the problems of data integrity that we mentioned earlier are solved . But todays personal computers, departmental com

30、puters, and distributed processing require computers and their applications to communicate with each other on a more equal or peer-to-peer basis. In a database, the client/server model provides the framework for distributing databases.One way to take advantage of many connected computers running dat

31、abase applications is to distribute the application into cooperating parts that are independent of one anther. A client is an end user or computer program that requests resources across a network. A server is a computer running software that fulfills those requests across a network . When the resour

32、ces are data in a database ,the client/server model provides the framework for distributing database.A file serve is software that provides access to files across a network. A dedicated file server is a single computer dedicated to being a file server. This is useful ,for example ,if the files are l

33、arge and require fast access .In such cases, a minicomputer or mainframe would be used as a file server. A distributed file server spreads the files around on individual computers instead of placing them on one dedicated computer.Advantages of the latter server include the ability to store and retri

34、eve files on other computers and the elimination of duplicate files on each computer. A major disadvantage , however, is that individual read/write requests are being moved across the network and problems can arise when updating files. Suppose a user requests a record from a file and changes it whil

35、e another user requests the same record and changes it too. The solution to this problems called record locking, which means that the first request makes others requests wait until the first request is satisfied . Other users may be able to read the record, but they will not be able to change it .A

36、database server is software that services requests to a database across a network. For example, suppose a user types in a query for data on his or her personal computer . If the application is designed with the client/server model in mind ,the query language part on the personal computer simple send

37、s the query across the network to the database server and requests to be notified when the data are found.Examples of distributed database systems can be found in the engineering world. Suns Network Filing System(NFS),for example, is used in computer-aided engineering applications to distribute data

38、 among the hard disks in a network of Sun workstation.Distributing databases is an evolutionary step because it is logical that data should exist at the location where they are being used . Departmental computers within a large corporation ,for example, should have data reside locally , yet those da

39、ta should be accessible by authorized corporate management when they want to consolidate departmental data . DBMS software will protect the security and integrity of the database , and the distributed database will appear to its users as no different from the non-distributed database .數(shù)據(jù)庫(kù)管理系統(tǒng)的介紹Ragh

40、u Ramakrishnan數(shù)據(jù)庫(kù)（database,有時(shí)拼作data base）又稱為電子數(shù)據(jù)庫(kù)，是專門組織起來(lái)的一組數(shù)據(jù)或信息，其目的是為了便于計(jì)算機(jī)快速查詢及檢索。數(shù)據(jù)庫(kù)的結(jié)構(gòu)是專門設(shè)計(jì)的，在各種數(shù)據(jù)處理操作命令的支持下，可以簡(jiǎn)化數(shù)據(jù)的存儲(chǔ)，檢索，修改和刪除。數(shù)據(jù)庫(kù)可以存儲(chǔ)在磁盤，磁帶，光盤或其他輔助存儲(chǔ)設(shè)備上。數(shù)據(jù)庫(kù)由一個(gè)或一套文件組成，其中的信息可以分解為記錄，每一記錄又包含一個(gè)或多個(gè)字段（或稱為域）。字段是數(shù)據(jù)存取的基本單位。數(shù)據(jù)庫(kù)用于描述實(shí)體，其中的一個(gè)字段通常表示與實(shí)體的某一屬性相關(guān)的信息。通過(guò)關(guān)鍵字以及各種分類（排序）命令，用戶可以對(duì)多條記錄的字段進(jìn)行查詢，重新整理，分組或選

41、擇，以實(shí)體對(duì)某一類數(shù)據(jù)的檢索，也可以生成報(bào)表。所有數(shù)據(jù)庫(kù)（最簡(jiǎn)單的除外）中都有復(fù)雜的數(shù)據(jù)關(guān)系及其鏈接。處理與創(chuàng)建，訪問(wèn)以及維護(hù)數(shù)據(jù)庫(kù)記錄有關(guān)的復(fù)雜任務(wù)的系統(tǒng)軟件包叫做數(shù)據(jù)庫(kù)管理系統(tǒng)（DBMS）。DBMS軟件包中的程序在數(shù)據(jù)庫(kù)與其用戶間建立接口。（這些用戶可以是應(yīng)用程序員，管理員及其他需要信息的人員和各種操作系統(tǒng)程序）。DBMS可組織，處理和表示從數(shù)據(jù)庫(kù)中選出的數(shù)據(jù)元。該功能使決策者能搜索，探查和查詢數(shù)據(jù)庫(kù)的內(nèi)容，從而對(duì)在正規(guī)報(bào)告中沒(méi)有的，不再出現(xiàn)的且無(wú)法預(yù)料的問(wèn)題做出回答。這些問(wèn)題最初可能是模糊的并且（或者）是定義不恰當(dāng)?shù)?，但是人們可以瀏覽數(shù)據(jù)庫(kù)直到獲得所需的信息。簡(jiǎn)言之，DBMS將“管理”存

42、儲(chǔ)的數(shù)據(jù)項(xiàng)，并從公共數(shù)據(jù)庫(kù)中匯集所需的數(shù)據(jù)項(xiàng)以回答非程序員的詢問(wèn)。DBMS由3個(gè)主要部分組成：（1）存儲(chǔ)子系統(tǒng)，用來(lái)存儲(chǔ)和檢索文件中的數(shù)據(jù)；（2）建模和操作子系統(tǒng)，提供組織數(shù)據(jù)以及添加，刪除，維護(hù)，更新數(shù)據(jù)的方法；（3）用戶和DBMS之間的接口。在提高數(shù)據(jù)庫(kù)管理系統(tǒng)的價(jià)值和有效性方面正在展現(xiàn)以下一些重要發(fā)展趨勢(shì)；1.管理人員需要最新的信息以做出有效的決策。2.客戶需要越來(lái)越復(fù)雜的信息服務(wù)以及更多的有關(guān)其訂單，發(fā)票和賬號(hào)的當(dāng)前信息。3.用戶發(fā)現(xiàn)他們可以使用傳統(tǒng)的程序設(shè)計(jì)語(yǔ)言，在很短的一段時(shí)間內(nèi)用數(shù)據(jù)庫(kù)系統(tǒng)開發(fā)客戶應(yīng)用程序。4.商業(yè)公司發(fā)現(xiàn)了信息的戰(zhàn)略價(jià)值，他們利用數(shù)據(jù)庫(kù)系統(tǒng)領(lǐng)先于競(jìng)爭(zhēng)對(duì)手。數(shù)據(jù)庫(kù)

43、中數(shù)據(jù)的性質(zhì)1.數(shù)據(jù)整體性：數(shù)據(jù)庫(kù)是一個(gè)單位或是一個(gè)應(yīng)用領(lǐng)域的通用數(shù)據(jù)處理系統(tǒng)，他存儲(chǔ)的是屬于企業(yè)和事業(yè)部門、團(tuán)體和個(gè)人的有關(guān)數(shù)據(jù)的集合。數(shù)據(jù)庫(kù)中的數(shù)據(jù)是從全局觀點(diǎn)出發(fā)建立的，他按一定的數(shù)據(jù)模型進(jìn)行組織、描述和存儲(chǔ)。其結(jié)構(gòu)基于數(shù)據(jù)間的自然聯(lián)系，從而可提供一切必要的存取路徑，且數(shù)據(jù)不再針對(duì)某一應(yīng)用，而是面向全組織，具有整體的結(jié)構(gòu)化特征。 2.數(shù)據(jù)共享性：數(shù)據(jù)庫(kù)中的數(shù)據(jù)是為眾多用戶所共享其信息而建立的，已經(jīng)擺脫了具體程序的限制和制約。不同的用戶可以按各自的用法使用數(shù)據(jù)庫(kù)中的數(shù)據(jù)；多個(gè)用戶可以同時(shí)共享數(shù)據(jù)庫(kù)中的數(shù)據(jù)資源，即不同的用戶可以同時(shí)存取數(shù)據(jù)庫(kù)中的同一個(gè)數(shù)據(jù)。數(shù)據(jù)共享性不僅滿足了各用戶對(duì)信息內(nèi)

44、容的要求，同時(shí)也滿足了各用戶之間信息通信的要求。數(shù)據(jù)管理的誕生數(shù)據(jù)庫(kù)的歷史可以追溯到五十年前，那時(shí)的數(shù)據(jù)管理非常簡(jiǎn)單。通過(guò)大量的分類、比較和表格繪制的機(jī)器運(yùn)行數(shù)百萬(wàn)穿孔卡片來(lái)進(jìn)行數(shù)據(jù)的處理，其運(yùn)行結(jié)果在紙上打印出來(lái)或者制成新的穿孔卡片。而數(shù)據(jù)管理就是對(duì)所有這些穿孔卡片進(jìn)行物理的儲(chǔ)存和處理。然而，1 9 5 1 年雷明頓蘭德公司（Remington Rand Inc.）的一種叫做Univac I 的計(jì)算機(jī)推出了一種一秒鐘可以輸入數(shù)百條記錄的磁帶驅(qū)動(dòng)器，從而引發(fā)了數(shù)據(jù)管理的革命。1956 年IBM生產(chǎn)出第一個(gè)磁盤驅(qū)動(dòng)器 the Model 305 RAMAC。此驅(qū)動(dòng)器有50 個(gè)盤片，每個(gè)盤片直徑是

45、2 英尺，可以儲(chǔ)存5MB的數(shù)據(jù)。使用磁盤最大的好處是可以隨機(jī)地存取數(shù)據(jù)，而穿孔卡片和磁帶只能順序存取數(shù)據(jù)。 1951： Univac系統(tǒng)使用磁帶和穿孔卡片作為數(shù)據(jù)存儲(chǔ)。 數(shù)據(jù)庫(kù)系統(tǒng)的萌芽出現(xiàn)于60 年代。當(dāng)時(shí)計(jì)算機(jī)開始廣泛地應(yīng)用于數(shù)據(jù)管理，對(duì)數(shù)據(jù)的共享提出了越來(lái)越高的要求。傳統(tǒng)的文件系統(tǒng)已經(jīng)不能滿足人們的需要。能夠統(tǒng)一管理和共享數(shù)據(jù)的數(shù)據(jù)庫(kù)管理系統(tǒng)（DBMS）應(yīng)運(yùn)而生。數(shù)據(jù)模型是數(shù)據(jù)庫(kù)系統(tǒng)的核心和基礎(chǔ)，各種DBMS 軟件都是基于某種數(shù)據(jù)模型的。所以通常也按照數(shù)據(jù)模型的特點(diǎn)將傳統(tǒng)數(shù)據(jù)庫(kù)系統(tǒng)分成網(wǎng)狀數(shù)據(jù)庫(kù)、層次數(shù)據(jù)庫(kù)和關(guān)系數(shù)據(jù)庫(kù)三類。 最早出現(xiàn)的是網(wǎng)狀 DBMS，是美國(guó)通用電氣公司Bachman等

46、人在1961年開發(fā)成功的IDS（Integrated DataStore）。1961年通用電氣公司（General ElectricCo.）的Charles Bachman 成功地開發(fā)出世界上第一個(gè)網(wǎng)狀DBMS也是第一個(gè)數(shù)據(jù)庫(kù)管理系統(tǒng) 集成數(shù)據(jù)存儲(chǔ)（Integrated DataStore IDS），奠定了網(wǎng)狀數(shù)據(jù)庫(kù)的基礎(chǔ)，并在當(dāng)時(shí)得到了廣泛的發(fā)行和應(yīng)用。IDS 具有數(shù)據(jù)模式和日志的特征。但它只能在GE主機(jī)上運(yùn)行，并且數(shù)據(jù)庫(kù)只有一個(gè)文件，數(shù)據(jù)庫(kù)所有的表必須通過(guò)手工編碼來(lái)生成。之后，通用電氣公司一個(gè)客戶BF Goodrich Chemical 公司最終不得不重寫了整個(gè)系統(tǒng)。并將重寫后的系統(tǒng)命名為

47、集成數(shù)據(jù)管理系統(tǒng)（IDMS）。 網(wǎng)狀數(shù)據(jù)庫(kù)模型對(duì)于層次和非層次結(jié)構(gòu)的事物都能比較自然的模擬，在關(guān)系數(shù)據(jù)庫(kù)出現(xiàn)之前網(wǎng)狀DBMS要比層次DBMS用得普遍。在數(shù)據(jù)庫(kù)發(fā)展史上，網(wǎng)狀數(shù)據(jù)庫(kù)占有重要地位。 層次型DBMS是緊隨網(wǎng)絡(luò)型數(shù)據(jù)庫(kù)而出現(xiàn)的。最著名最典型的層次數(shù)據(jù)庫(kù)系統(tǒng)是IBM 公司在1968 年開發(fā)的IMS （Information Management System），一種適合其主機(jī)的層次數(shù)據(jù)庫(kù)。這是IBM公司研制的最早的大型數(shù)據(jù)庫(kù)系統(tǒng)程序產(chǎn)品。從60 年代末產(chǎn)生起，如今已經(jīng)發(fā)展到IMSV6，提供群集、N路數(shù)據(jù)共享、消息隊(duì)列共享等先進(jìn)特性的支持。這個(gè)具有3 0 年歷史的數(shù)據(jù)庫(kù)產(chǎn)品在如今的WWW應(yīng)

48、用連接、商務(wù)智能應(yīng)用中扮演著新的角色。 1973 年Cullinane 公司（也就是后來(lái)的Cullinet軟件公司），開始出售Goodrich 公司的IDMS 改進(jìn)版本，并且逐漸成為當(dāng)時(shí)世界上最大的軟件公司。關(guān)系數(shù)據(jù)庫(kù)的由來(lái)網(wǎng)狀數(shù)據(jù)庫(kù)和層次數(shù)據(jù)庫(kù)已經(jīng)很好地解決了數(shù)據(jù)的集中和共享問(wèn)題，但是在數(shù)據(jù)獨(dú)立性和抽象級(jí)別上仍有很大欠缺。用戶在對(duì)這兩種數(shù)據(jù)庫(kù)進(jìn)行存取時(shí)，仍然需要明確數(shù)據(jù)的存儲(chǔ)結(jié)構(gòu)，指出存取路徑。而后來(lái)出現(xiàn)的關(guān)系數(shù)據(jù)庫(kù)較好地解決了這些問(wèn)題。 1970年，IBM關(guān)系模型的概念，奠定了關(guān)系模型的理論基礎(chǔ)。盡管之前在1968年Childs已經(jīng)提出了面向集合的模型，然而這篇論文被普遍認(rèn)為是數(shù)據(jù)庫(kù)系統(tǒng)歷

49、史上具有劃時(shí)代意義的里程碑。Codd的心愿是為數(shù)據(jù)庫(kù)建立一個(gè)優(yōu)美的數(shù)據(jù)模型。后來(lái)Codd又陸續(xù)發(fā)表多篇文章，論述了范式理論和衡量關(guān)系系統(tǒng)的12條標(biāo)準(zhǔn)，用數(shù)學(xué)理論奠定了關(guān)系數(shù)據(jù)庫(kù)的基礎(chǔ)。關(guān)系模型有嚴(yán)格的數(shù)學(xué)基礎(chǔ)，抽象級(jí)別比較高，而且簡(jiǎn)單清晰，便于理解和使用。但是當(dāng)時(shí)也有人認(rèn)為關(guān)系模型是理想化的數(shù)據(jù)模型，用來(lái)實(shí)現(xiàn) DBMS是不現(xiàn)實(shí)的，尤其擔(dān)心關(guān)系數(shù)據(jù)庫(kù)的性能難以接受，更有人視其為當(dāng)時(shí)正在進(jìn)行中的網(wǎng)狀數(shù)據(jù)庫(kù)規(guī)范化工作的嚴(yán)重威脅。為了促進(jìn)對(duì)問(wèn)題的理解，1974 年ACM牽頭組織了一次研討會(huì)，會(huì)上開展了一場(chǎng)分別以Codd和Bachman為首的支持和反對(duì)關(guān)系數(shù)據(jù)庫(kù)兩派之間的辯論。這次著名的辯論推動(dòng)了關(guān)系數(shù)

50、據(jù)庫(kù)的發(fā)展，使其最終成為現(xiàn)代數(shù)據(jù)庫(kù)產(chǎn)品的主流。 1969： Edgar F?！癟ed” Codd發(fā)明了關(guān)系數(shù)據(jù)庫(kù) 1970年關(guān)系模型建立之后，IBM公司在San Jose實(shí)驗(yàn)室增加了更多的研究人員研究這個(gè)項(xiàng)目，這個(gè)項(xiàng)目就是著名的System R。其目標(biāo)是論證一個(gè)全功能關(guān)系DBMS的可行性。該項(xiàng)目結(jié)束于1979年，完成了第一個(gè)實(shí)現(xiàn)SQL的 DBMS。然而IBM對(duì)IMS的承諾阻止了System R的投產(chǎn)，一直到1980年System R才作為一個(gè)產(chǎn)品正式推向市場(chǎng)。IBM產(chǎn)品化步伐緩慢的三個(gè)原因：IBM重視信譽(yù)，重視質(zhì)量，盡量減少故障；IBM是個(gè)大公司，官僚體系龐大；IBM內(nèi)部已經(jīng)有層次數(shù)據(jù)庫(kù)產(chǎn)品，

51、相關(guān)人員不積極，甚至反對(duì)。 然而同時(shí)，1973年加州大學(xué)伯克利分校的Michael Stonebraker和Eugene Wong利用System R已發(fā)布的信息開始開發(fā)自己的關(guān)系數(shù)據(jù)庫(kù)系統(tǒng)Ingres。他們開發(fā)的Ingres項(xiàng)目最后由Oracle公司、Ingres公司以及硅谷的其他廠商所商品化。后來(lái)，System R和Ingres系統(tǒng)雙雙獲得ACM的1988年“軟件系統(tǒng)獎(jiǎng)”。 1976年霍尼韋爾公司(Honeywell)開發(fā)了第一個(gè)商用關(guān)系數(shù)據(jù)庫(kù)系統(tǒng)Multics Relational Data Store。關(guān)系型數(shù)據(jù)庫(kù)系統(tǒng)以關(guān)系代數(shù)為堅(jiān)實(shí)的理論基礎(chǔ)，經(jīng)過(guò)幾十年的發(fā)展和實(shí)際應(yīng)用，技術(shù)越來(lái)越成

52、熟和完善。其代表產(chǎn)品有Oracle、IBM公司的 DB2、微軟公司的MS SQL Server以及Informix、ADABASD等等。結(jié)構(gòu)化查詢語(yǔ)言(SQL)1974 年，IBM的Ray Boyce和Don Chamberlin將Codd關(guān)系數(shù)據(jù)庫(kù)的12條準(zhǔn)則的數(shù)學(xué)定義以簡(jiǎn)單的關(guān)鍵字語(yǔ)法表現(xiàn)出來(lái)，里程碑式地提出了SQL(Structured Query Language)語(yǔ)言。SQL語(yǔ)言的功能包括查詢、操縱、定義和控制，是一個(gè)綜合的、通用的關(guān)系數(shù)據(jù)庫(kù)語(yǔ)言，同時(shí)又是一種高度非過(guò)程化的語(yǔ)言，只要求用戶指出做什么而不需要指出怎么做。SQL集成實(shí)現(xiàn)了數(shù)據(jù)庫(kù)生命周期中的全部操作。SQL提供了與關(guān)系數(shù)據(jù)

53、庫(kù)進(jìn)行交互的方法，它可以與標(biāo)準(zhǔn)的編程語(yǔ)言一起工作。自產(chǎn)生之日起，SQL語(yǔ)言便成了檢驗(yàn)關(guān)系數(shù)據(jù)庫(kù)的試金石，而SQL語(yǔ)言標(biāo)準(zhǔn)的每一次變更都指導(dǎo)著關(guān)系數(shù)據(jù)庫(kù)產(chǎn)品的發(fā)展方向。然而，直到二十世紀(jì)七十年代中期，關(guān)系理論才通過(guò)SQL在商業(yè)數(shù)據(jù)庫(kù)Oracle和DB2中使用。 1986年，ANSI把SQL作為關(guān)系數(shù)據(jù)庫(kù)語(yǔ)言的美國(guó)標(biāo)準(zhǔn)，同年公布了標(biāo)準(zhǔn)SQL文本。目前SQL標(biāo)準(zhǔn)有3個(gè)版本。基本SQL定義是ANSIX3135-89，“Database Language - SQL with Integrity Enhancement”ANS89，一般叫做SQL-89。SQL-89定義了模式定義、數(shù)據(jù)操作和事務(wù)處理。S

54、QL- 89和隨后的ANSIX3168-1989，“Database Language-Embedded SQL”構(gòu)成了第一代SQL標(biāo)準(zhǔn)。ANSIX3135-1992ANS92描述了一種增強(qiáng)功能的SQL，現(xiàn)在叫做SQL-92標(biāo)準(zhǔn)。SQL-92包括模式操作，動(dòng)態(tài)創(chuàng)建和SQL語(yǔ)句動(dòng)態(tài)執(zhí)行、網(wǎng)絡(luò)環(huán)境支持等增強(qiáng)特性。在完成SQL-92標(biāo)準(zhǔn)后，ANSI和ISO即開始合作開發(fā)SQL3標(biāo)準(zhǔn)。SQL3的主要特點(diǎn)在于抽象數(shù)據(jù)類型的支持，為新一代對(duì)象關(guān)系數(shù)據(jù)庫(kù)提供了標(biāo)準(zhǔn)。數(shù)據(jù)庫(kù)巨人的誕生甲骨文公司（Oracle） 數(shù)據(jù)庫(kù)管理項(xiàng)目和做顧問(wèn)咨詢工作。而IBM卻沒(méi)有計(jì)劃開發(fā)，為什么藍(lán)色巨人放棄了這個(gè)價(jià)值上百億的產(chǎn)品，原

55、因有很多：IBM的研究人員大多是學(xué)術(shù)出身，他們最感興趣的是理論，而非推向市場(chǎng)的產(chǎn)品，從學(xué)術(shù)上看，研究成果應(yīng)公開，發(fā)表論文和演講能使他們成名，為什么不呢？還有一個(gè)很主要的原因就是IBM 當(dāng)時(shí)有一個(gè)銷售得還不錯(cuò)的層次數(shù)據(jù)庫(kù)產(chǎn)品IMS。直到1985年I B M 才發(fā)布了關(guān)系數(shù)據(jù)庫(kù)D B 2 ,Ellision那時(shí)已經(jīng)成了千萬(wàn)富翁。Ellison曾將IBM 選擇Microsoft 的MS-DOS作為IBM-PC機(jī)的操作系統(tǒng)比為：“世界企業(yè)經(jīng)營(yíng)歷史上最嚴(yán)重的錯(cuò)誤，價(jià)值超過(guò)了上千億美元?！盜BM 發(fā)表R系統(tǒng)論文，而且沒(méi)有很快推出關(guān)系數(shù)據(jù)庫(kù)產(chǎn)品的錯(cuò)誤可能僅僅次之。Oracle 的市值在1996年就達(dá)到了28

56、0億美元。 面向?qū)ο髷?shù)據(jù)庫(kù)隨著信息技術(shù)和市場(chǎng)的發(fā)展，人們發(fā)現(xiàn)關(guān)系型數(shù)據(jù)庫(kù)系統(tǒng)雖然技術(shù)很成熟，但其局限性也是顯而易見(jiàn)的：它能很好地處理所謂的“表格型數(shù)據(jù)”，卻對(duì)技術(shù)界出現(xiàn)的越來(lái)越多的復(fù)雜類型的數(shù)據(jù)無(wú)能為力。九十年代以后，技術(shù)界一直在研究和尋求新型數(shù)據(jù)庫(kù)系統(tǒng)。但在什么是新型數(shù)據(jù)庫(kù)系統(tǒng)的發(fā)展方向的問(wèn)題上，產(chǎn)業(yè)界一度是相當(dāng)困惑的。受當(dāng)時(shí)技術(shù)風(fēng)潮的影響，在相當(dāng)一段時(shí)間內(nèi)，人們把大量的精力花在研究“面向?qū)ο蟮臄?shù)據(jù)庫(kù)系統(tǒng)(object oriented database)”或簡(jiǎn)稱“OO數(shù)據(jù)庫(kù)系統(tǒng)”。值得一提的是，美國(guó)Stonebraker教授提出的面向?qū)ο蟮年P(guān)系型數(shù)據(jù)庫(kù)理論曾一度受到產(chǎn)業(yè)界的青睞。而Ston

57、ebraker本人也在當(dāng)時(shí)被Informix花大價(jià)錢聘為技術(shù)總負(fù)責(zé)人。 然而，數(shù)年的發(fā)展表明，面向?qū)ο蟮年P(guān)系型數(shù)據(jù)庫(kù)系統(tǒng)產(chǎn)品的市場(chǎng)發(fā)展的情況并不理想。理論上的完美性并沒(méi)有帶來(lái)市場(chǎng)的熱烈反應(yīng)。其不成功的主要原因在于，這種數(shù)據(jù)庫(kù)產(chǎn)品的主要設(shè)計(jì)思想是企圖用新型數(shù)據(jù)庫(kù)系統(tǒng)來(lái)取代現(xiàn)有的數(shù)據(jù)庫(kù)系統(tǒng)。這對(duì)許多已經(jīng)運(yùn)用數(shù)據(jù)庫(kù)系統(tǒng)多年并積累了大量工作數(shù)據(jù)的客戶，尤其是大客戶來(lái)說(shuō)，是無(wú)法承受新舊數(shù)據(jù)間的轉(zhuǎn)換而帶來(lái)的巨大工作量及巨額開支的。另外，面向?qū)ο蟮年P(guān)系型數(shù)據(jù)庫(kù)系統(tǒng)使查詢語(yǔ)言變得極其復(fù)雜，從而使得無(wú)論是數(shù)據(jù)庫(kù)的開發(fā)商家還是應(yīng)用客戶都視其復(fù)雜的應(yīng)用技術(shù)為畏途。 數(shù)據(jù)管理的變革二十世紀(jì)六十年代后期出現(xiàn)了一種新型數(shù)

58、據(jù)庫(kù)軟件：決定支持系統(tǒng)(DSS)，其目的是讓管理者在決策過(guò)程中更有效地利用數(shù)據(jù)信息。于是在1970年， 第一個(gè)聯(lián)機(jī)分析處理工具Express誕生了。其他決策支持系統(tǒng)緊隨其后，許多是由公司的IT部門開發(fā)出來(lái)的。 1985年，第一個(gè)商務(wù)智能系統(tǒng)(business intelligence)由Metaphor計(jì)算機(jī)系統(tǒng)有限公司為Procter & Gamble公司開發(fā)出來(lái)，主要是用來(lái)連接銷售信息和零售的掃描儀數(shù)據(jù)。同年， Pilot 軟件公司開始出售第一個(gè)商用客戶/服務(wù)器執(zhí)行信息系統(tǒng)Command Center。同樣在這年，加州大學(xué)伯克利分校Ingres項(xiàng)目演變成Postgres，其目標(biāo)是開發(fā)出一個(gè)面向?qū)ο蟮臄?shù)據(jù)庫(kù)。此后一年， Graphael公司開發(fā)了第一個(gè)商用的對(duì)象數(shù)據(jù)庫(kù)系統(tǒng)Gbase。 1988年，IBM公司的研究者Barry Devlin和Paul Murphy發(fā)明了一個(gè)新的術(shù)語(yǔ)信息倉(cāng)庫(kù)，之后，IT的廠商開始構(gòu)建實(shí)驗(yàn)性的數(shù)據(jù)倉(cāng)庫(kù)。1991年，W.H. "Bill" Inmon出版了一本“如何構(gòu)建數(shù)據(jù)倉(cāng)庫(kù)”的書，使得數(shù)據(jù)倉(cāng)庫(kù)真正開始應(yīng)用。 1991： W.H.“Bill” Inmon發(fā)表了”構(gòu)建數(shù)據(jù)倉(cāng)庫(kù)” 二十世紀(jì)九十年代，隨著基于PC的客戶/服務(wù)器計(jì)算模式和企業(yè)軟件包的廣泛采用，數(shù)據(jù)管理的變革基本完成。數(shù)據(jù)管理不再僅僅