數(shù)據(jù)庫(kù)管理-外文翻譯

1、<p>　　畢業(yè)論文（設(shè)計(jì)）外文翻譯</p><p>　　題 目： 新生入學(xué)管理系統(tǒng) </p><p>　　學(xué) 院： </p><p>　　學(xué)生姓名： </p><p>　　專(zhuān) 業(yè)： </p><p>　

2、　班 級(jí)： </p><p>　　指導(dǎo)教師： </p><p><b>　　起止日期： </b></p><p><b>　　年月日</b></p><p>　　Database Management</p><p&g

3、t;　　Database (sometimes spelled database) is also called an electronic database, referring to any collections of data, or information, that is specially organized for rapid search and retrieval by a computer. Databases a

4、re structured to facilitate the storage, retrieval modification and deletion of data in conjunction with various data-processing operations. Database can be stored on magnetic disk or tape, optical disk, or some other se

5、condary storage device.</p><p>　　A database consists of a file or a set of files. The information in the these files may be broken down into records, each of which consists of one or more fields are the basi

6、c 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 commands, users can rapidly search,

7、 rearrange, group, and select the fields in many records to retrieve or create reports on particular aggre</p><p>　　Database records and files must be organized to allow retrieval of the information. Early s

8、ystem were arranged sequentially (i.e., alphabetically, numerically, or chronologically); the development of direct-access storage devices made possible random access to data via indexes. Queries are the main way users r

9、etrieve database information. Typically the user provides a string of characters, and the computer searches the database for a corresponding sequence and provides the source materials in wh</p><p>　　The many

10、 users of a large database must be able to manipulate the information within it quickly at any given time. Moreover, large business and other organizations tend to build up many independent files containing related and e

11、ven overlapping data, and their data, processing activities often require the linking of data from several files. Several different types of database management systems have been developed to support these requirements:

12、flat, hierarchical, network, relational, and object-</p><p>　　In flat databases, records are organized according to a simple list of entities; many simple databases for personal computers are flat in structu

13、re. The records in hierarchical databases are organized in a treelike structure, with each level of records branching off into a set of smaller categories. Unlike hierarchical databases, which provide single links betwee

14、n sets of records at different levels, network databases create multiple linkages between sets by placing links, or pointers, to one se</p><p>　　The information in many databases consists of natural-language

15、 texts of documents; number-oriented database primarily contain information such as statistics, tables, financial data, and raw scientific and technical data. Small databases can be maintained on personal-computer system

16、s and may be used by individuals at home. These and larger databases have become increasingly important in business life. Typical commercial applications include airline reservations, production management, medical rec&l

17、t;/p><p><b>　　數(shù)據(jù)庫(kù)管理</b></p><p>　　數(shù)據(jù)庫(kù)（有時(shí)拼成Database）也稱(chēng)為電子數(shù)據(jù)庫(kù)，是計(jì)算機(jī)為解決特定的任務(wù),以一定的組織方式存儲(chǔ)在一起的相關(guān)的數(shù)據(jù)的集合。數(shù)據(jù)庫(kù)與其它數(shù)據(jù)處理操作協(xié)同工作，其結(jié)構(gòu)要有助于數(shù)據(jù)的存儲(chǔ)、檢索、修改和刪除。數(shù)據(jù)庫(kù)可存儲(chǔ)在磁盤(pán)或磁帶、光盤(pán)或某些輔助存儲(chǔ)設(shè)備上。</p><p>　　一個(gè)

18、數(shù)據(jù)庫(kù)由一個(gè)文件或文件集合組成。這些文件中的信息可分解成一個(gè)個(gè)記錄，每個(gè)記錄有一個(gè)或多個(gè)域。域是數(shù)據(jù)庫(kù)存儲(chǔ)的基本單位，每個(gè)域一般含有由數(shù)據(jù)庫(kù)描述的屬于實(shí)體的一個(gè)方面或一個(gè)特性的信息。用戶使用鍵盤(pán)和各種排序命令，能夠快速查找、重排、分組并在查找的許多記錄中選擇相應(yīng)的域，建立特定集上的報(bào)表。 </p><p>　　數(shù)據(jù)庫(kù)的記錄和文件必須被組織起來(lái)，以確保能對(duì)信息進(jìn)行檢索。早期的系統(tǒng)是順序組織的（如:字母順序、數(shù)字順序

19、或時(shí)間順序）；直接訪問(wèn)存儲(chǔ)設(shè)備的研制成功使得通過(guò)索引隨機(jī)訪問(wèn)數(shù)據(jù)成為可能。用戶檢索數(shù)據(jù)庫(kù)信息的主要方法是query（查詢）。通常情況下，用戶提供一個(gè)字符串，計(jì)算機(jī)在數(shù)據(jù)庫(kù)中尋找相應(yīng)的字符序列，并且給出字符串在何處出現(xiàn)。比如，用戶必須能在任意給定的時(shí)間內(nèi)，能夠快速處理內(nèi)部數(shù)據(jù)。而且，大型企業(yè)和其它組織傾向于建立許多獨(dú)立的文件，其中包含相互關(guān)聯(lián)的甚至重疊的數(shù)據(jù)，這些數(shù)據(jù)、處理活動(dòng)經(jīng)常需要和其它文件的數(shù)據(jù)相連。為滿足這些要求，開(kāi)發(fā)出各種不同類(lèi)

20、型的數(shù)據(jù)庫(kù)管理系統(tǒng)，如：非結(jié)構(gòu)化的數(shù)據(jù)庫(kù)、層次型數(shù)據(jù)庫(kù)、網(wǎng)絡(luò)型數(shù)據(jù)庫(kù)、關(guān)系型數(shù)據(jù)庫(kù)、面向?qū)ο笮蛿?shù)據(jù)庫(kù)。</p><p>　　在非結(jié)構(gòu)化的數(shù)據(jù)庫(kù)中，按照實(shí)體的一個(gè)簡(jiǎn)單列表組織記錄，很多個(gè)人計(jì)算機(jī)的簡(jiǎn)易數(shù)據(jù)庫(kù)就是非結(jié)構(gòu)的。層次型數(shù)據(jù)庫(kù)按樹(shù)型組織記錄，每一層的記錄分解成更小的屬性集。層次型數(shù)據(jù)庫(kù)在不同層的記錄集之間提供一個(gè)單一鏈接。與此不同，網(wǎng)絡(luò)型數(shù)據(jù)庫(kù)在不同記錄集之間提供多個(gè)鏈接，這是通過(guò)設(shè)置指向其它記錄集的鏈或指針

21、來(lái)實(shí)現(xiàn)的。網(wǎng)絡(luò)型數(shù)據(jù)庫(kù)的速度及多樣性使其在企業(yè)中得到廣泛應(yīng)用。當(dāng)文件或記錄間的關(guān)系不能用鏈表達(dá)時(shí)，使用關(guān)系型數(shù)據(jù)庫(kù)。一個(gè)表或一個(gè)“關(guān)系”，就是一個(gè)簡(jiǎn)單的非結(jié)構(gòu)列表。多個(gè)關(guān)系可通過(guò)數(shù)學(xué)關(guān)系提供所需信息。面向?qū)ο蟮臄?shù)據(jù)庫(kù)存儲(chǔ)并處理更復(fù)雜的稱(chēng)為對(duì)象的數(shù)據(jù)結(jié)構(gòu)，可組織成有層次的類(lèi)，其中的每個(gè)類(lèi)可以繼承層次鏈中更高一級(jí)類(lèi)的特性，這種數(shù)據(jù)庫(kù)結(jié)構(gòu)最靈活，最具適應(yīng)性。</p><p>　　很多數(shù)據(jù)庫(kù)包含自然語(yǔ)言文本信息，可由個(gè)人

22、在家中使用。小型及稍大的數(shù)據(jù)庫(kù)在商業(yè)領(lǐng)域中占有越來(lái)越重要的地位。典型的商業(yè)應(yīng)用包括航班預(yù)訂、產(chǎn)品管理、醫(yī)院的醫(yī)療記錄以及保險(xiǎn)公司的合法記錄。最大型的數(shù)據(jù)庫(kù)通常用天政府部門(mén)、企業(yè)、大專(zhuān)院校等。這些數(shù)據(jù)庫(kù)存有諸如摘要、報(bào)表、成文的法規(guī)、通訊錄、報(bào)紙、雜志、百科全書(shū)、各式目錄等資料。索引數(shù)據(jù)庫(kù)包含參考書(shū)目或用于找到相關(guān)書(shū)籍、期刊及其它參考文獻(xiàn)的索引。目前有上萬(wàn)種可公開(kāi)訪問(wèn)的數(shù)據(jù)庫(kù)，內(nèi)容包羅萬(wàn)象，從法律、醫(yī)學(xué)、工程到新聞、時(shí)事、游戲、分類(lèi)廣告、

23、指南等?？茖W(xué)家、醫(yī)生、律師、財(cái)經(jīng)分析師、股票經(jīng)紀(jì)人等專(zhuān)家和各類(lèi)研究者越來(lái)越多地依賴這些數(shù)據(jù)庫(kù)從大量的信息中做快速的查找訪問(wèn)。</p><p>　　DBMS Structuring Techniques</p><p>　　Sequential, direct, and other file processing approaches are used to organize and str

24、ucture data in single files. But a DBMS is able to integrate data elements from several files to answer specific user inquiries for information. That is, the DBMS is able to structure and tie together the logically relat

25、ed data from several large files. </p><p>　　Logical Structures. Identifying these logical relationships is a job of the data administrator. A data definition language is used for this purpose. The DBMS may t

26、hen employ one of the following logical structuring techniques during storage access, and retrieval operations.</p><p>　　List structures. In this logical approach, records are linked together by the use of p

27、ointers. A pointer is a data item in one record that identifies the storage location of another logically related record. Records in a customer master file, for example, will contain the name and address of each customer

28、, and each record in this file is identified by an account number. During an accounting period, a customer may buy a number of items on different days. Thus, the company may maintain an invoice </p><p>　　Hie

29、rarchical (tree) structures. In this logical approach, data units are structured in multiple levels that graphically resemble an “upside down” tree with the root at the top and the branches formed below. There’s a superi

30、or-subordinate relationship in a hierarchical (tree) structure. Below the single-root data component are subordinate elements or nodes, each of which, in turn, “own” one or more other elements (or none). Each element or

31、branch in this structure below the root has only a single</p><p>　　Network Structures. Unlike the tree approach, which does not permit the connection of branches, the network structure permits the connection

32、 of the nodes in a multidirectional manner. Thus, each node may have several owners and may, in turn, own any number of other data units. Data management software permits the extraction of the needed information from suc

33、h a structure by beginning with any record in a file.</p><p>　　Relational structures. A relational structure is made up of many tables. The data are stored in the form of “relations” in these tables. For exa

34、mple, relation tables could be established to link a college course with the instructor of the course, and with the location of the class.</p><p>　　To find the name of the instructor and the location of the

35、English class, the course/instructor relation is searched to get the name (“Fit”), and the course/location relation is a relatively new database structuring approach that’s expected to be widely implemented in the future

36、.</p><p>　　Physical Structures. People visualize or structure data in logical ways for their own purposes. Thus, records R1 and R2 may always be logically linked and processed in sequence in one particular a

37、pplication. However, in a computer system it’s quite possible that these records that are logically contiguous in one application are not physically stored together. Rather, the physical structure of the records in media

38、 and hardware may depend not only on the I/O and storage devices and techniques used</p><p>　　數(shù)據(jù)庫(kù)管理系統(tǒng)的組織技術(shù)</p><p>　　順序的、直接的以及其他的文件處理方式常用于單個(gè)文件中數(shù)據(jù)的組織和構(gòu)造，而DBMS可綜合幾個(gè)文件的數(shù)據(jù)項(xiàng)以回答用戶對(duì)信息的查詢，這就意味著DBMS能夠訪問(wèn)和檢

39、索非關(guān)鍵記錄字段的數(shù)據(jù)，即DBMS能夠?qū)讉€(gè)大文件夾中邏輯相關(guān)的數(shù)據(jù)組織并連接在一起。</p><p>　　邏輯結(jié)構(gòu)。確定這些邏輯關(guān)系是數(shù)據(jù)管理者的任務(wù)，由數(shù)據(jù)定義語(yǔ)言完成。DBMS在存儲(chǔ)、訪問(wèn)和檢索操作過(guò)程中可選用以下邏輯構(gòu)造技術(shù)：</p><p>　　鏈表結(jié)構(gòu)。在該邏輯方式中，記錄通過(guò)指針鏈接在一起。指針是記錄本中的一個(gè)相數(shù)據(jù)項(xiàng)，它指出另一個(gè)邏輯相關(guān)的記錄的存儲(chǔ)位置，例如，顧客主文件中

40、的記錄將包含每個(gè)顧客的姓名和地址，而且該文件中的每個(gè)記錄都由一個(gè)賬號(hào)標(biāo)識(shí)。在記賬期間，顧客可在不同時(shí)間購(gòu)買(mǎi)許多東西。公司保存一個(gè)發(fā)票文件以反映這下地交易，這種情況下可使用鏈表結(jié)構(gòu)，以顯示給定時(shí)間內(nèi)未支付的發(fā)票。顧客文件中的每個(gè)記錄都包含這樣一個(gè)字段，該字段指向發(fā)票文件中該顧客的第一個(gè)發(fā)票的記錄位置，該發(fā)票記錄又依次與該顧客的下一個(gè)發(fā)票記錄相連，此鏈接的最后一個(gè)發(fā)票記錄由一個(gè)作為指針的特殊字符標(biāo)識(shí)。</p><p>

41、;　　層次（樹(shù)型）結(jié)構(gòu)。該邏輯方式中，數(shù)據(jù)單元的多級(jí)結(jié)構(gòu)類(lèi)似一棵“倒立”的樹(shù)，該樹(shù)的樹(shù)根在頂部，而樹(shù)枝向下延伸。在層次（樹(shù)型）結(jié)構(gòu)中存在主-從關(guān)系，惟一的根數(shù)據(jù)下是從屬的元或節(jié)點(diǎn)，而每個(gè)元或樹(shù)枝都只有一個(gè)所有者，這樣，一個(gè)customer（顧客）擁有一個(gè)invoice（發(fā)票），而invoice（發(fā)票）又有從屬項(xiàng)。在樹(shù)型結(jié)構(gòu)中，樹(shù)枝不能相連。</p><p>　　網(wǎng)狀結(jié)構(gòu)。網(wǎng)狀結(jié)構(gòu)不像樹(shù)型結(jié)構(gòu)那樣不允許樹(shù)枝相連，它

42、允許節(jié)點(diǎn)間多個(gè)方向連接，這樣，每個(gè)節(jié)點(diǎn)都可能有幾個(gè)所有者，中央電視臺(tái)它又可能擁有任意多個(gè)其他數(shù)據(jù)單元。數(shù)據(jù)管理軟件允許從文件的任一記錄開(kāi)始提取該結(jié)構(gòu)中的所需信息。</p><p>　　關(guān)系型結(jié)構(gòu)。關(guān)系型結(jié)構(gòu)由許多表格組成，數(shù)據(jù)則以“關(guān)系”的形式存儲(chǔ)在這些表中。例如，可建立一些關(guān)系表，將大學(xué)課程同任課教師及上課地點(diǎn)連接起來(lái)。為了找到英語(yǔ)課的上課地點(diǎn)和教師名，首先查詢課程/教師關(guān)系表得到名字（為“Fit”），再查詢課

43、程/地點(diǎn)關(guān)系表得到地點(diǎn)（“Main 142”），當(dāng)然，也可能有其他關(guān)系。這是一個(gè)相當(dāng)新穎的數(shù)據(jù)庫(kù)組織技術(shù)，將來(lái)有望得到廣泛應(yīng)用。</p><p>　　物理結(jié)構(gòu)。人們總是為了各自的目的，按邏輯方式設(shè)想或組織數(shù)據(jù)。因此，在一個(gè)具體應(yīng)用中，記錄R1和R2是邏輯相連且順序處理的，但是，在計(jì)算機(jī)系統(tǒng)中，這些在一個(gè)應(yīng)用中邏輯相鄰的記錄，物理位置完全可能不在一起。記錄在介質(zhì)和硬件中的物理結(jié)構(gòu)不僅取決于所采用的I/O設(shè)備、存儲(chǔ)設(shè)