数据库 毕业论文外文翻译.doc

英文原文及中文翻译database一、database management systems (dbms) andmanagement information system (mis)you know that a database is a collection of logically related data elements that may be structured in various ways to meet the multiple processing and retrieval needs of organizations and individuals. theres nothing new about databases-early ones were chiseled in stone, penned on scrolls, and written on index cards. but now databases are commonly recorded on magnetically media, and computer programs are required to perform the necessary storage and retrieval operations.youll see in the following pages that complex data relationships and linkages may be found in all but the simplest databases. the system software package that handles the difficult tasks associated 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 information needs, and various os programs. )a dbms can organize, process, and present selected data elements from 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 in 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 queries of those who arent programmers. in a file-oriented system, users needing special information may communicate their needs to a programmer, who, when time permits, will write one or more programs to extract the data and prepare the informationc4. the availability of a dbms, however, offers users a much faster alternative communications path (see fig. 7-1).the management information system (mis) concept has been defined in dozens of ways. since one organizations model of an mis is likely to differ from that of another, its not surprising that their mis definitions would also vary in scope and breadth. for our purposes, an mis can be defined as a network of computer-based data processing procedures developed in an organization and 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.although mis models differ, most of them recognize the concepts shown in fig. 7-2. in addition to what might be termed the horizontal management structure shown in fig. 7-2(a), an organization is also divided vertically into different specialities and functions which require separate information flows (see fig. 7-2 (b). combining the horizontal managerial levels with the vertical specialities produces the complex organizational structure shown in fig. 7-2(e). underlying this structure is a database consisting, ideally, of internally and externally produced data relating to past, present, and predicted furture events.the formidable task of the mis designer is to develop the information flow needed to support decision making (see fig. 7-3) generally speaking, much of the information needed by managers who occupy different levels and who have different responsibilities is obtained from a collection of existing information systems (or subsystems) . these systems may be tied together very closely in an mis. more often, however, they are more loosely coupled.二、sql and sql serveribm invented a computer language back in the 1970s designed specifically for database queries called sequei.; those letters stand for structured english query language. over time, the language has been added to so that it is not just a language for queries, but can also build databases and manage the database engines security. ibm released sequel. into the public domain, where it became known as sql. because of this heritage you can pronounce it sequel or spell it out s-q-i. there are various versions of sql used in todays database engines. microsoft sql server uses a version called transact-sql, or t-sql, which stands for transaction sql.1. what is sql server?sql server is a client/server relational database management system (rdbms) that uses transact-sql. to send requests between a client and sql. server.2. client/server architecturethe terms client, server, and client/server can be used to refer to very general concepts or to specific items of hardware or software. at the most general level, a client is any component of a system that requests services or resources from other components of a system. a server is any component of a system that provides services or resources to other components of a system.for example, when you print a document from your workstation on a network, the workstation is the client and the machine that does the print spooling is the server, any client/server data-based system consists of the following components:the server-a collection of data items and supporting objects organized and presented to facilitate services, such as searching, sorting, recombining, retrieving, updating, and analyzing data. the database consists of the physical storage of data and the database services. all data access occurs through the server; the physical data is never accessed directly by the client.the client-a software program that might be used interactively by a person or that could be an automated process. this includes all software that interacts with the server, either requesting data from or sending data to the database. examples are management utilities (those that are part of the sql server product as well as those bought separately), ad hoc query and reporting software, custom applications, off-the-shelf applications, and web server-based applications. the communication between the client and the server-the communication between the client and the server depends largely on how the client and server are implemented. both physical and logical layers of communication can be identified.when you communicate with someone using the telephone, the telephone system is the physical layer and a spoken natural language is the logical layer of communication.for a data-based system, the physical layer can be a network if the server and the client are on different computers. it can be inter process communication if the server and the client are on the same computer. the logical communication structure of the physical layer may be low-level operating system calls, a proprietary data access language, or the open structured query language (sql).3. sql server platformssql. server runs on the operating systems shown in fig. 7-4. the sql. server version 7 server software runs only on the windows 32-bit ah-based operating systems, but you can use all of the operating system platforms to create and execute client applications.三、data warehouseit is often said, the age of the industrial revolution has finally been completed and the world has entered the age of the information technology revolution(see fig. 7-5). it is our belief that the need for data warehouse applications is one of the manifestations of this information technology age. a data warehouse is becoming more of a necessity than an accessory for a progressive, competitive, and focused organization. it provides the right foundation for building decision support and executive information system tools that are often built to measure and provide a feel for how well an organization is progressing toward its goals.1. collecting operational dataadvances in computer and networking technology have led to the introduction of very powerful hardware and software platforms that can collect, manage, and distrihute large amounts of pertinent data. in the case of a business application, detailed transactions are often generated during product-or service-related interactions. these transactions are not limited to commercial sectors. they are also found in sectors such as, government, health care, insurance, manufacturing, finance, distribution, education, and so on. any enterprise that has some computerized record keeping systems and is interested in deducting or drawing logical conclusions from their voluminous, granular, and detailed information pool should consider building an enterprise-level data warehouse application. these enterprises will then be capable of improving their insights into the trends in their operations and eventually increase the accuracy of their forecasts and plans. the effectiveness of the data warehouse application intensifies especially when the operational data resides in distributed, nonhomogenous systems and replace manual data gathering and reconciliation procedures.operational data is the highly structured sets of information that support the ongoing and day-to-day operation o an organization. in case of a decentralized organization, operational data is generated at remote locations sometimes in no homogeneous distributed systems (see fig. 7-6). distributed systems can span many different geographical locations and time zones. they are configured to provide scalability, visibility, and tracking capabilities of business processes. for instance, the order is entered by a customer representative in one site. the financial state of the order is verified at another site. once approved, it is forwarded to manufacturing to be assembled. finally, the shipping staff is alerted to fulfill the order that was booked at the remote sitecs3. standard reports or ad hoc queries that inquire about the details of these events are typical examples of operational reports. they are generated on a regular basis. any delay in their processing will have a significant disruption to the normal operation of that business.2. convergence of many computer technologiesthe infrastructure that supports the data warehouse application relies on the same technologies that most other applications are dependent upon. the difference is in the variety and specialization at the product level that can greatly improve the quality of the data warehouse infrastructure.below are some technologies that have made their mark in the data warehouse marketplace. in order to produce a data warehouse that best meets users needs, these underlining technologies have to be evaluated as part of the periodic resource capacity planning. depending upon the requirements and resources available, the best combination can be selected and configured.server technology. client technology. database management system (dbms) technology.networking technology. mass storage technology. data presentation and publication requirements.software engineering methodology and tools.common characteristics of a data warehouse(1) data is divided into three categories.(a) reference and transaction data. includes lists, charts, and transaction data from source systems. originally generated in the source systems. can be kept in the data warehouse or an operational data store system. is loaded into the data warehouse on a regular basis. should never change once in the data warehouse (data correction and refresh are exceptions). may be purged from the source. is archived in the data warehouse if purged from the source. (b) derived data. is based on the reference data and certain business rules.can always be re-created. business rules must be approved by end-users. (c) denormalized data. is based on the detailed reference data. is prepared periodically. is the foundation for olap tools.(2) enhancements are done in an iterative approach.(3) enhancements should be based on the overall architecture.(4) one end-user tool may not be adequate for all analytical needs. depending on the amount of data and type of queries, different end-user tools must be selected.(5) transaction-level database recovery is not necessary.(6) data warehouse platform should be tuned for performance rather than quick recovery purposes.数 据 库一、 数据库管理系统(dbms)和管理信息系统(mis)众所周知，数据库是逻辑上相关的数据元的汇集。这些数据元可以按不同的结构组织起来，以满足单位和个人的多种处理和检索的需要。数据库本身不是什么新鲜事早期的数据库凿在石头上，记在名册上，以及写在索引卡中。而现在，数据库普遍记录在可磁化的介质上，并且需要用计算机程序来执行必需的存储和检索操作。如下所述，所有数据库(最简单的除外)中都有复杂的数据关系及其链接。处理与创建、访问以及维护数据库记录有关的复杂任务的系统软件包叫做数据库管理系统(dbms)。dbms软件包中的程序在数据库与其用户间建立接口。(这些用户可以是应用程序员、管理员、及其他需要信息的人员和各种操作系统程序)。dbms可组织、处理和表示从数据库中选出的数据元。该功能使决策者能搜索、探查和查询数据库的内容，从而对在正规报告中没有的、不再出现的且无法预料的问题作出回答。这些问题最初可能是模糊的并且(或者)是定义不恰当的，但是人们可以浏览数据库直到获得所需的信息。简言之，dbms将“管理”存 储的数据项，并从公共数据库中汇集所需的数据项以回答非程序员的询问。在面向文件的系统中，需要特定信息的用户应将他们的要求传送给程序员。该程序员在时间允许时，将编写一个或多个程序以提取数据和准备信息。然而，dbms的可用性为用户提供了一个更快的替代通信通道(如图71所示)。管理信息系统(mis)的概念已经用数十种方式定义过。因为mis的组织模型可能各不相同，所以mis的定义随应用范围和广度而变化就不奇怪了。本文认为，mis系统可定义为基于计算机的数据处理过程的网络系统，它是一个机构为了支持决策及其他必需的管理功能提供及时有效的信息而开发的，并且可按需要把人工和其他过程结合在一起。 尽管mis模型不同，但其中大多数都认可如图?2所示的概念。除图72(a)中所示的横向管理结 构如何命名之外，一个机构从纵向也可分成需要独立信息流的不同职能部门(见图72(b)。综合横向管理级和纵向特长产生了如图72(c)所示的复杂组织结构。这个结构的基础是数据库，该数据库理想的方式是由内部和外部产生的，与过去、现在及预见到的将来事件相关的数据组成。mis设计者的一个棘手的问题是开发支持决策所需的信息流(见图73)。一般而言，不同级别与不同职责的管理者所需的信息大多来自现有信息系统(或子系统)的汇集，这些系统在mis中可紧密地结合在一起，但是，更经常的情况是松散耦合的。二、 sql和sql服务器ibm在20世纪70年代，设计了一种专门处理数据库查询的计算机语言sequei,这几个字母是结构化英语查询语言的缩写。随着时间的推移，它增加了许多功能，就不仅是一个查询语言了，还可以创建数据库，管理数据库引擎的安全。ibm把它公开发行，于是就变成了现在为大家所知的sql由于历史的原因sql可以读成sequel，也可以逐字段拼成sql。在现在的数据库引擎里，已经有了好多种sqi。版本。微软sql server使用的是t-sql，它代表的是事务sqi。1什么是sql server?sql server是一个客户机g艮务器关系型数据库管理系统(rdbms)，它使用事务sql在客户机和sql服务器间传送请求。2客户机服务器体系结构术语客户机、服务器和客户机服务器可以是非常广的概念或专指硬件、软件。按最一般的概念。客户机是从系统其他部件请求服务或资源的系统的任何部件；服务器是向系统其他部件提供服务或资源的任何部件。例如，当用户从网络上的工作站打印一个文件时，工作站是客户机，用作假脱机打印的机器是服务器。任何基于数据的客户机、服务器系统都由下列部件组成。服务器数据项和支持对象的汇集，其中这些对象是有组织的并随时准备提交，以便为数据的搜索、分类、重组、检索、更新和分析之类的服务提供便利。数据库由数据的物理存储器和数据库服务组成。所有的数据访问都通过服务器进行，客户机一概不能直接访问物理数据。客户机一一个软件程序，该程序应该由个人交互使用或可能是一个自动进程。其中包括从数据库请求数据，或向数据库送数的与服务器交互作用的所有软件，例如管理实用程序(这些是sql服务器产品的一部分并且是单独购买的)、特别查询和报告软件、客户应用程序、现货应用程序和基于web服务器的应用程序。客户机和服务器之间的通信客户机和服务器之间的通信在很大程度上取决于客户和服务器是如何实现的。通信的物理层和逻辑层可能是一样的。当你用电话与某人通信时，电话系统是物理层，所讲的自然语言是通信的逻辑层。对于基于数据的系统，如果服务器和客户在不同的计算机：，则物理层可以是网络。如果服务器和客户在同一台计算机上，则通信可在进程之