數(shù)據(jù)庫(kù)畢業(yè)設(shè)計(jì)外文文獻(xiàn)及翻譯

1、<p><b>　　外文文獻(xiàn)原稿和譯文</b></p><p><b>　　原 稿</b></p><p><b>　　DATABASE</b></p><p>　　A database may be defined as a collection interrelated data st

2、ore together with as little redundancy as possible to serve one or more applications in an optimal fashion .the data are stored so that they are independent of programs which use the data .A common and controlled approac

3、h is used in adding new data and in modifying and retrieving existing data within the data base .One system is said to contain a collection of database if they are entirely separate in structure .</p><p>　　A

4、 database may be designed for batch processing , real-time processing ,or in-line processing .A data base system involves application program, DBMS, and database. </p><p>　　THE INTRODUCTION TO DATABASE MANAG

5、EMENT SYSTEMS</p><p>　　The term database is often to describe a collection of related files that is organized into an integrated structure that provides different people varied access to the same data. In ma

6、ny cases this resource is located in different files in different departments throughout the organization, often known only to the individuals who work with their specific portion of the total information. In these cases

7、, the potential value of the information goes unrealized because a person in other departments w</p><p>　　A database is a collection of related data. By data, we mean known facts that can be recorded and tha

8、t have implicit meaning. For example, the names, telephone numbers, and addresses of all the people you know. You may have recorded this data in an indexed address book, or you may have stored it on a diskette using a pe

9、rsonal computer and software such as DBASE Ⅲ or Lotus 1-2-3. This is a collection of related data with an implicit meaning and hence is a database.</p><p>　　The above definition of database is quite general.

10、 For example, we may consider the collection of words that made up this page of text to be usually more restricted. A database has the following implicit properties:</p><p>　　A database is a logically cohere

11、nt collection of data with some inherent meaning. A random assortment of data cannot be referred to as a database.</p><p>　　A database is designed, built, and populated with data for a specific purpose. It h

12、as an intended group of user and some preconceived applications in which these users are interested.</p><p>　　A database represents some aspect of the real world, sometimes called the miniworld. Changes to t

13、he miniworld are reflected in the database.</p><p>　　In other words, a database has some source from which data are derived, some degree of interaction with events in the real world, and an audience that is

14、actively interested in the contents of the database.</p><p>　　A database management system (DBMS) is composed of three major parts: (1) a storage subsystem that stores and retrieves data in files; (2)a model

15、ing and manipulation subsystem that provides the means with which to organize the data and to add, delete, maintain, and update the data; and (3) an interface between the DBMS and its users. Several major trends are emer

16、ging that enhance the value and usefulness of database management systems.</p><p>　　Managers who require more up-to-date information to make effective decisions.</p><p>　　Customers who demand in

17、creasingly sophisticated information services and more current information about the status of their orders, invoices, and accounts.</p><p>　　Users who find that they can develop custom applications with dat

18、abase systems in a fraction of the time it takes to use traditional programming languages.</p><p>　　Organizations that discover information has a strategic value; they utilize their database systems to gain

19、an edge over their competitors.</p><p>　　A DBMS can organize, process, and present selected data elements from the database. This capability enables decision makers to search, probe, and query data base cont

20、ents in order to extract answers to nonrecurring and unplanned questions that aren’t available in regular reports. These questions might initially be vague and/or poorly defined, but people can “browse” through the datab

21、ase until they have the needed information. In short, the DBMS will “mange” the stored data items and assemble the</p><p>　　DATABASE QUERY </p><p>　　If the DBMS provides a way to interactively e

22、nter and update the database ,as well as interrogate it ,this capability allows for managing personal database. However, it does not automatically leave an audit trail of actions and does not provide the kinds of control

23、s necessary in a multi-user organization .There controls are only available when a set of application programs is customized for each data entry and updating function.</p><p>　　Software for personal computer

24、s that perform some of the DBMS functions has been very popular .Individuals for personal information storage and processing intended personal computers for us .Small enterprises, professionals like doctors, architects,

25、engineers, lawyers and so on have also used these machines extensively. By the nature of intended usage ,database system on there machines are except from several of the requirements of full-fledged database systems. Sin

26、ce data sharing is not intende</p><p>　　DBMS STRUCTURING TECHNIQUES </p><p>　　Spatial data management has been an active area of research in the database field for two decades ,with much of the

27、research being focused on developing data structures for storing and indexing spatial data .however, no commercial database system provides facilities for directly de fining and storing spatial data ,and formulating quer

28、ies based on research conditions on spatial data.</p><p>　　There are two components to data management: history data management and version management .Both have been the subjects of research for over a deca

29、de. The troublesome aspect of temporal data management is that the boundary between applications and database systems has not been clearly drawn. Specifically, it is not clear how much of the typical semantics and facil

30、ities of temporal data management can and should be directly incorporated in a database system, and how much should be left to appli</p><p>　　The focus of research into history data management has been on de

31、fining the semantics of time and time interval, and issues related to understanding the semantics of queries and updates against history data stored in an attribute of a record. Typically, in the context of relational da

32、tabases ,a temporal attribute is defined to hold a sequence of history data for the attribute. A history data consists of a data item and a time interval for which the data item is valid. A query may then be issued</

33、p><p>　　In the absence of a support for temporal attributes, application developers who need to model and history data have simply simulated temporal attributes by creating attribute for the time interval ,alon

34、g with the “temporal” attribute. This of course may result in duplication of records in a table, and more complicated search predicates in queries. The one necessary topic of research in history data management is to qua

35、ntitatively establish the performance (and even productivity) differences betw</p><p>　　Data security, integrity, and independence</p><p>　　Data security prevents unauthorized users from viewing

36、 or updating the database. Using passwords, users are allowed access to the entire database of the database, called subschemas. For example, an employee database can contain all the data about an individual employee, but

37、 one group of users may be authorized to view only payroll data, while others are allowed access to only work history and medical data.</p><p>　　Data integrity refers to the accuracy, correctness, or validit

38、y of the data in the database. In a database system, data integrity means safeguarding the data against invalid alteration or destruction. In large on-line database system, data integrity becomes a more severe problem an

39、d two additional complications arise. The first has to do with many users accessing the database concurrently. For example, if thousands of travel agents book the same seat on the same flight, the first agent’s booking&l

40、t;/p><p>　　The second complication relates to hardware, software or human error during the course of processing and involves database transaction which is a group of database modifications treated as a single u

41、nit. For example, an agent booking an airline reservation involves several database updates (i.e., adding the passenger’s name and address and updating the seats-available field), which comprise a single transaction. The

42、 database transaction is not considered to be completed until all updates have be</p><p>　　An important point about database systems is that the database should exist independently of any of the specific app

43、lications. Traditional data processing applications are data dependent.</p><p>　　When a DMBS is used, the detailed knowledge of the physical organization of the data does not have to be built into every appl

44、ication program. The application program asks the DBMS for data by field name, for example, a coded representation of “give me customer name and balance due” would be sent to the DBMS. Without a DBMS the programmer must

45、reserve space for the full structure of the record in the program. Any change in data structure requires changes in all the applications programs.</p><p>　　Data Base Management System (DBMS)</p><p

46、>　　The system software package that handles the difficult tasks associated with creating ,accessing and maintaining data base records is called a data base management system (DBMS). A DBMS will usually be handing mult

47、iple data calls concurrently.It must organize its system buffers so that different data operations can be in process together .It provides a data definition language to specify the conceptual schema and most likely ,some

48、 of the details regarding the implementation of the conceptual sch</p><p>　　List structures.</p><p>　　Relational structures.</p><p>　　Hierarchical (tree) structures.</p><

49、p>　　Network structures.</p><p>　　Management Information System(MIS) </p><p>　　An MIS can be defined as a network of computer-based data processing procedures developed in an organization and

50、integrated as necessary with manual and other procedures for the purpose of providing timely and effective information to support decision making and other necessary management functions.</p><p>　　One of the

51、 most difficult tasks of the MIS designer is to develop the information flow needed to support decision making .Generally speaking ,much of the information needed by managers who occupy different levels and who have diff

52、erent levels and have different responsibilities is obtained from a collection of exiting information system (or subsystems)</p><p>　　Structure Query Language (SQL)</p><p>　　SQL is a data base p

53、rocessing language endorsed by the American National Standards Institute. It is rapidly becoming the standard query language for accessing data on relational databases .With its simple ,powerful syntax ,SQL represents a

54、great progress in database access for all levels of management and computing professionals.</p><p>　　SQL falls into two forms : interactive SQL and embedded SQL. Embedded SQL usage is near to traditional pro

55、gramming in third generation languages .It is the interactive use of SQL that makes it most applicable for the rapid answering of ad hoc queries .With an interactive SQL query you just type in a few lines of SQL and you

56、get the database response immediately on the screen.</p><p><b>　　譯 文</b></p><p><b>　　數(shù)據(jù)庫(kù)</b></p><p>　　數(shù)據(jù)庫(kù)可以被定義為一個(gè)相互聯(lián)系的數(shù)據(jù)庫(kù)存儲(chǔ)的集合。這個(gè)集合有很少的冗余，盡可能的為一個(gè)或多個(gè)疑難公用程序在最

57、理想的方式下服務(wù)。數(shù)據(jù)存書(shū)的目的是使他們用數(shù)據(jù)程序獨(dú)立，一種通用且受控制的方法用于數(shù)據(jù)庫(kù)內(nèi)增加新數(shù)據(jù)、修復(fù)和恢復(fù)已存在的數(shù)據(jù)。如果一個(gè)系統(tǒng)在結(jié)構(gòu)上完全分離，則它們被稱(chēng)為包含一個(gè)數(shù)據(jù)庫(kù)集合。</p><p>　　一個(gè)數(shù)據(jù)庫(kù)可以設(shè)計(jì)為批處理、實(shí)時(shí)處理或聯(lián)機(jī)處理，一個(gè)數(shù)據(jù)庫(kù)系統(tǒng)包括應(yīng)用程序、數(shù)據(jù)庫(kù)管理系統(tǒng)和數(shù)據(jù)庫(kù)。</p><p><b>　　數(shù)據(jù)庫(kù)管理系統(tǒng)簡(jiǎn)介</b>&l

58、t;/p><p>　　數(shù)據(jù)庫(kù)這個(gè)詞經(jīng)常用來(lái)描述相關(guān)文件的集合,這些文件被編成一個(gè)完整的復(fù)雜結(jié)構(gòu)，這個(gè)結(jié)構(gòu)對(duì)于相同的數(shù)據(jù)為不同的人提供不同的渠道。在許多情況下，這些資源被放在機(jī)構(gòu)的不同部門(mén)的不同文件中，通常只為那些與特定信息打交道的人所知。在這些情況下，信息的潛在價(jià)值沒(méi)有實(shí)現(xiàn)，因?yàn)槠渌块T(mén)需要它的人卻不知道這些信息，或者不能有效地訪問(wèn)這些信息。為了管理制鞋信息資源，并提供及時(shí)高效的訪問(wèn)，許多公司建立書(shū)記庫(kù)。</p

59、><p>　　數(shù)據(jù)庫(kù)是相關(guān)數(shù)據(jù)的集合。數(shù)據(jù)，是指已知的可以被記錄并且有固定意義的事實(shí)。例如，所有你知道的人的名字、電話號(hào)碼和地址，可以在一個(gè)索引地址簿中記錄，或者可以用個(gè)人衛(wèi)星計(jì)算機(jī)及諸如dBASE Ⅲ 或Lotus 1-2-3這樣的軟件把它們記錄在軟盤(pán)上。這是一個(gè)相關(guān)并且具有內(nèi)在意義的集合，因而它是一個(gè)數(shù)據(jù)庫(kù)。</p><p>　　上面的數(shù)據(jù)庫(kù)的定義是相當(dāng)一般性的。例如，我們可以認(rèn)為組成這頁(yè)

60、文字的詞的集合是相關(guān)數(shù)據(jù)，因而稱(chēng)之為數(shù)據(jù)庫(kù)。然而，作為通用的數(shù)據(jù)庫(kù)術(shù)語(yǔ)常常是有一些限制的，數(shù)據(jù)庫(kù)有下列內(nèi)在的性質(zhì)：</p><p>　　數(shù)據(jù)庫(kù)是在邏輯上緊密相關(guān)的并且有某種內(nèi)在意義的集合，隨機(jī)的數(shù)據(jù)組合不能稱(chēng)為數(shù)據(jù)庫(kù)；</p><p>　　數(shù)據(jù)庫(kù)是為某種特定目的而設(shè)計(jì)、建議和聚集的數(shù)據(jù)，它有一些預(yù)期的用戶和這些用戶感興趣的某些預(yù)想的應(yīng)用；</p><p>　　數(shù)據(jù)庫(kù)

61、表示實(shí)際世界某一方面，有時(shí)也叫做“微型世界”，對(duì)微型世界的改變反映在數(shù)據(jù)庫(kù)中。</p><p>　　換言之，數(shù)據(jù)庫(kù)有某種“源”，有與真實(shí)世界的一些事件在某種程度上的交互，有對(duì)數(shù)據(jù)庫(kù)的內(nèi)容非常關(guān)注的使用者。</p><p>　　數(shù)據(jù)庫(kù)管理系統(tǒng)（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；

62、（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)：</p><p>　　管理人員需要最新的信息發(fā)作出有效的決策；</p><p>　　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；</p><p>　　用戶發(fā)現(xiàn)他們可以使用傳統(tǒng)的程序設(shè)計(jì)語(yǔ)言在很短的一從段時(shí)間內(nèi)用數(shù)據(jù)庫(kù)系統(tǒng)開(kāi)發(fā)客戶應(yīng)用程序；&

63、lt;/p><p>　　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。</p><p>　　數(shù)據(jù)庫(kù)管理信息系統(tǒng)可組織、處理和顯示從數(shù)據(jù)庫(kù)中選擇的數(shù)據(jù)元素。這種能力使決策者可以搜索、探測(cè)和查詢數(shù)據(jù)庫(kù)的內(nèi)容，從而對(duì)在正式報(bào)告中沒(méi)有的、有再出現(xiàn)的且無(wú)計(jì)劃的問(wèn)題作出回答。這些問(wèn)題最初可能是模糊的或者還是定義不清的，但是人們可以瀏覽數(shù)據(jù)庫(kù)獲得所需要的信息。簡(jiǎn)言之，DBMS將“管理”存儲(chǔ)

64、的數(shù)據(jù)項(xiàng)，并從公共數(shù)據(jù)庫(kù)中匯集所需要的數(shù)據(jù)項(xiàng)來(lái)回答那些非程序員的詢問(wèn)。在面向文件的系統(tǒng)中，需要特定信息的用戶可以將他們的要求傳送給那些程序員，該程序員在時(shí)間允許時(shí)，將編寫(xiě)一個(gè)或多個(gè)程序以提取數(shù)據(jù)和準(zhǔn)備信息。但是，使用DBMS可以為用戶提供一種更快的、可由用戶選擇的通信方式。</p><p><b>　　數(shù)據(jù)庫(kù)查詢</b></p><p>　　如果數(shù)據(jù)庫(kù)管理信息系統(tǒng)提供

65、一種進(jìn)入和修改數(shù)據(jù)庫(kù)，以及查詢數(shù)據(jù)庫(kù)的交互方法，這種方法就是為管理個(gè)人數(shù)據(jù)庫(kù)蟹黃早了條件。但是，它不能自動(dòng)進(jìn)行跟蹤查詢，也不能在多用戶組織中提供那種必要的控制。只有當(dāng)一組程序?yàn)槊恳粋€(gè)數(shù)據(jù)進(jìn)入和更新功能定制客戶規(guī)格是，才有可能得到這些控制。</p><p>　　當(dāng)前，執(zhí)行數(shù)據(jù)庫(kù)管理系統(tǒng)某些功能的個(gè)人計(jì)算機(jī)軟件一直都很流行。個(gè)人計(jì)算機(jī)是用來(lái)進(jìn)行個(gè)人信息存儲(chǔ)和處理的。這些機(jī)器也廣泛的被一些小企業(yè)、職業(yè)家如醫(yī)生、建筑師、

66、工程師、律師等所用。從使用意圖的性質(zhì)看，這些機(jī)器上的數(shù)據(jù)庫(kù)系統(tǒng)中沒(méi)有正式數(shù)據(jù)庫(kù)的一些要求。由于不需要數(shù)據(jù)共享，也不需要同時(shí)操作，軟件也就不那么復(fù)雜。安全和整體維護(hù)也不那么重要，甚至沒(méi)有。隨著數(shù)據(jù)容量變小，性能效率也不那么重要。事實(shí)上，數(shù)據(jù)庫(kù)系統(tǒng)唯一重要的方向是數(shù)據(jù)獨(dú)立性。正如以前所述，數(shù)據(jù)獨(dú)立性是指在輔助存儲(chǔ)器上，應(yīng)用程序和用戶詢問(wèn)不必了解數(shù)據(jù)的物理組織。這個(gè)方面的重要性，尤其對(duì)個(gè)人計(jì)算機(jī)用戶來(lái)說(shuō)，大大簡(jiǎn)化了數(shù)據(jù)庫(kù)的使用。用戶能夠高層次

67、的存儲(chǔ)、訪問(wèn)和操縱數(shù)據(jù)庫(kù)，并且能夠完全不受數(shù)據(jù)庫(kù)組織低層次細(xì)節(jié)的影響。</p><p><b>　　DBMS 結(jié)構(gòu)技術(shù)</b></p><p>　　二十年來(lái)空間數(shù)據(jù)管理一直是數(shù)據(jù)庫(kù)研究的活躍區(qū)，研究的焦點(diǎn)集中在發(fā)展存儲(chǔ)和索引空間數(shù)據(jù)的數(shù)據(jù)結(jié)構(gòu)上。但是，還沒(méi)有商業(yè)數(shù)據(jù)庫(kù)系統(tǒng)產(chǎn)品可用來(lái)直接確定和存儲(chǔ)空間數(shù)據(jù)以及基于空間數(shù)據(jù)的研究條件的公式化查詢。</p>&

68、lt;p>　　時(shí)間數(shù)據(jù)管理有兩個(gè)組成部分：歷史數(shù)據(jù)管理和版本管理。這兩種管理十多年來(lái)一直是研究的對(duì)象。時(shí)間數(shù)據(jù)管理方面的麻煩是：應(yīng)用和數(shù)據(jù)庫(kù)系統(tǒng)之間的界限還沒(méi)有劃清楚，特別是時(shí)間數(shù)據(jù)管理的典型語(yǔ)義和設(shè)備由多少能夠且應(yīng)該直接合并在數(shù)據(jù)庫(kù)系統(tǒng)中，有多少應(yīng)該留給應(yīng)用和用戶，還不十分清楚。本章將提供一個(gè)研究問(wèn)題的目錄，應(yīng)該檢查目錄以說(shuō)明這一基本問(wèn)題。]</p><p>　　研究歷史數(shù)據(jù)庫(kù)的焦點(diǎn)是確定時(shí)間和時(shí)間間隔的

69、語(yǔ)義，并且了解查詢和更改存儲(chǔ)在記錄中的歷史數(shù)據(jù)的語(yǔ)義問(wèn)題。典型的說(shuō)，在關(guān)系數(shù)據(jù)庫(kù)中，時(shí)間屬性被確定為持有一定順序的具有屬性的歷史數(shù)據(jù)，一個(gè)歷史數(shù)據(jù)是由數(shù)據(jù)項(xiàng)目和對(duì)數(shù)據(jù)項(xiàng)目的有效的時(shí)間間隔組成。在給定的時(shí)間間隔，就會(huì)產(chǎn)生一次查詢，即為該特定時(shí)間間隔而檢索歷史數(shù)據(jù)。支持時(shí)間屬性的作用相似于支持?jǐn)?shù)據(jù)庫(kù)系統(tǒng)中的定值屬性，例如像UniSQL 那樣。</p><p>　　在時(shí)間屬性沒(méi)有被支持的情況下，需要模擬和管理歷史數(shù)據(jù)，

70、應(yīng)用程序開(kāi)發(fā)者通過(guò)為時(shí)間間隔及時(shí)間屬性創(chuàng)造屬性而簡(jiǎn)單的模擬屬性。這當(dāng)然可能會(huì)在表格中導(dǎo)致記錄的復(fù)制及查詢更加復(fù)雜的搜索依據(jù)。在有關(guān)歷史研究的數(shù)據(jù)管理中，一個(gè)必要的研究課題是定量的分析使用直接支持時(shí)間屬性的數(shù)據(jù)庫(kù)系統(tǒng)合使用不支持時(shí)間屬性的常見(jiàn)數(shù)據(jù)庫(kù)系統(tǒng)之間的性能（甚至效率）差別數(shù)據(jù)。</p><p>　　數(shù)據(jù)的安全性、完整性和獨(dú)立性</p><p>　　數(shù)據(jù)安全是要防止未經(jīng)批準(zhǔn)的用戶瀏覽和修

71、改數(shù)據(jù)庫(kù)。只有使用密碼，用戶才被允許訪問(wèn)數(shù)據(jù)庫(kù)或數(shù)據(jù)庫(kù)子集。例如，一個(gè)雇員阿湖據(jù)庫(kù)包含關(guān)于雇員個(gè)人的全部數(shù)據(jù)，但是只允許一組用戶查看一個(gè)工資單數(shù)據(jù)，而其他用戶只允許查看歷史和醫(yī)療方面的數(shù)據(jù)。</p><p>　　數(shù)據(jù)完整性指數(shù)據(jù)庫(kù)中數(shù)據(jù)的精確度、正確性或合法性。在數(shù)據(jù)庫(kù)系統(tǒng)中，數(shù)據(jù)的完整性意味著保護(hù)數(shù)據(jù)不被非法修改或破壞。在大型聯(lián)機(jī)數(shù)據(jù)庫(kù)系統(tǒng)中，數(shù)據(jù)的完整性更為重要，并且還存在另外兩個(gè)復(fù)雜的問(wèn)題：一是不得不考慮多

72、個(gè)用戶同時(shí)訪問(wèn)數(shù)據(jù)庫(kù)，例如，如果上千個(gè)旅行社代理預(yù)約了同一航班，統(tǒng)一座位的機(jī)票，這樣的話第一個(gè)代理人的預(yù)定將丟失，在這種情況下，采用封鎖記錄或字段的技術(shù)就可以保護(hù)用戶正在修改的記錄不被其他用戶訪問(wèn)。</p><p>　　第二個(gè)問(wèn)題與硬件、軟件或處理過(guò)程中人為錯(cuò)誤有關(guān)，它包含是數(shù)據(jù)庫(kù)始終保持完整性的數(shù)據(jù)庫(kù)事務(wù)。數(shù)據(jù)庫(kù)事務(wù)是一組視作整體的數(shù)據(jù)庫(kù)修改工作，如一個(gè)旅行社代理人預(yù)定一個(gè)航班，預(yù)約就包括幾個(gè)數(shù)據(jù)庫(kù)的修改（即增

73、加乘客的姓名和地址，并修改可用作為字段）這些修改組成了一個(gè)事務(wù)。只有當(dāng)所有修改執(zhí)行完畢后，才認(rèn)為該數(shù)據(jù)庫(kù)事務(wù)完成，否則不允許再進(jìn)行其他任何修改。</p><p>　　數(shù)據(jù)庫(kù)系統(tǒng)指公關(guān)重要的一點(diǎn)是數(shù)據(jù)庫(kù)應(yīng)獨(dú)立于任何一個(gè)具體的應(yīng)用。傳統(tǒng)的數(shù)據(jù)庫(kù)處理應(yīng)用是數(shù)據(jù)相關(guān)的。</p><p>　　當(dāng)一個(gè)數(shù)據(jù)庫(kù)管理系統(tǒng)被使用時(shí)，有關(guān)數(shù)據(jù)管理組織的詳細(xì)情況不必建立在每一個(gè)應(yīng)用程序中。應(yīng)用程序通過(guò)字段名向數(shù)據(jù)

74、庫(kù)管理系統(tǒng)查詢數(shù)據(jù)。例如，一個(gè)代碼表示的“將客戶名稱(chēng)和應(yīng)付余額給我”的語(yǔ)句會(huì)被送進(jìn)數(shù)據(jù)庫(kù)管理系統(tǒng)中。如果沒(méi)有數(shù)據(jù)管理信息系統(tǒng)，程序員必須給程序中記錄的全部結(jié)構(gòu)留下空間。數(shù)據(jù)結(jié)構(gòu)的任何變化要求所有的應(yīng)用程序作相應(yīng)的變化。</p><p>　　數(shù)據(jù)庫(kù)管理系統(tǒng)（DBMS）</p><p>　　處理與創(chuàng)建、訪問(wèn)及維護(hù)數(shù)據(jù)庫(kù)激勵(lì)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）。一個(gè)數(shù)據(jù)庫(kù)管理

75、系統(tǒng)通常是用于處理多個(gè)數(shù)據(jù)調(diào)用，它必須組織系統(tǒng)緩沖以使不同的數(shù)據(jù)庫(kù)操作能夠一起處理，他提供一種數(shù)據(jù)定義語(yǔ)言以制定概念模式，很可能還包括用物理模式實(shí)現(xiàn)概念模式的一些細(xì)節(jié)。數(shù)據(jù)定義語(yǔ)言是一種高級(jí)語(yǔ)言，能夠借用數(shù)據(jù)模型描述概念模型。</p><p>　　目前，數(shù)據(jù)庫(kù)管理系統(tǒng)有4種主要的基本結(jié)構(gòu)，它們是：</p><p><b>　　表結(jié)構(gòu)。</b></p>&

76、lt;p><b>　　關(guān)系結(jié)構(gòu)。</b></p><p>　　層次結(jié)構(gòu)（樹(shù)結(jié)構(gòu)。網(wǎng)絡(luò)結(jié)構(gòu)。）</p><p>　　管理信息系統(tǒng)（MIS）</p><p>　　一個(gè)MIS可定義為一個(gè)基于計(jì)算機(jī)的數(shù)據(jù)處理過(guò)程的網(wǎng)絡(luò)系統(tǒng)，一個(gè)機(jī)構(gòu)為了支持決策及其他必須的管理功能，以便提供及時(shí)有效的信息，開(kāi)發(fā)了這一系統(tǒng)；若需要，手工操作與其過(guò)程也在該系統(tǒng)中結(jié)合在

77、一起了。MIS設(shè)計(jì)者的一個(gè)難題是分析支持決策所需的信息流。一般而言，不同的管理者和各種職責(zé)的管理者所需的信息大多來(lái)自現(xiàn)有的信息系統(tǒng)（或子系統(tǒng)）集。</p><p>　　SQL是美國(guó)國(guó)家標(biāo)準(zhǔn)學(xué)會(huì)認(rèn)可的數(shù)據(jù)處理語(yǔ)言。它正迅速成為在相關(guān)數(shù)據(jù)庫(kù)中存取數(shù)據(jù)的標(biāo)準(zhǔn)詢問(wèn)語(yǔ)言。由于其簡(jiǎn)潔有力的語(yǔ)法功能，SQL的產(chǎn)生是各管理層及計(jì)算行業(yè)在數(shù)據(jù)庫(kù)中存取數(shù)據(jù)的一次飛躍。</p><p>　　SQL有兩種形式：交