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1、扬州大学计算机专业毕业设计( 外文翻译 ) 1 外文资料Database Management SystemsA 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 facilitat
2、e 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 these file
3、s 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 commands, use
4、rs 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 associat
5、ed 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 informati
6、on 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 aren t available in r
7、egular 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 quer
8、ies of those who aren t 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, an
9、d 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; 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 1 页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 2 Managers: who require more up-to-data informa
10、tion to make effective decision Customers: who demand increasingly sophisticated information 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 ta
11、kes to use traditional programming languages. Organizations : that discover information has a strategic value; they utilize their database systems to gain an edge over their competitors. The Database Model A data model describes a way to structure and manipulate the data in a database. The structura
12、l part of the model specifies how data should be represented(such as tree, tables, and so 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 ModelThe first database management sys
13、tems used a hierarchical model-that is-they arranged records into a tree structure. Some 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 acc
14、essed first, then records one level below the root ,and so on. The hierarchical model was 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 le
15、vel, middle management at lower levels, and operational employees at the lowest levels. Note 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-
16、many relationship among data. In the hierarchical approach, each relationship must be explicitly 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
17、data do not always conform to such a strict hierarchy. Relational Model A major breakthrough 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 data
18、base is the most widely used database structure. Data is organized into related tables. Each 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 精选学习资料 - - - - -
19、 - - - - 名师归纳总结 - - - - - - -第 2 页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 3 would contain fields of data such as a person s last name ,first name ,and street address. Structured query language(SQL)is a query language for manipulating data in a relational database .It is nonprocedural or declarative, in which t
20、he 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 description into a procedure to perform the database manipulation. Network Model The network model creates relationships among data
21、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. The pointers are addresses that indicate the location of a record. With the network approach, a subordinate record can be l
22、inked 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 other database models. Today , such performance characteristics are only important in high-volume ,high-speed transaction
23、processing such as automatic teller machine networks or airline reservation system. Both hierarchical and network databases are application specific. If a new application is developed ,maintaining the consistency of databases in different applications can be very difficult. For example, suppose a ne
24、w 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 which records are represented by entities called objects that can both store data and provide methods or procedures to perf
25、orm 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 because there is no simple , uniform query language such as SQL . The object model is relatively new, and only a few ex
26、amples 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-oriented model. Distributed Database Similarly , a distributed database is one in which different parts of the database reside
27、 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 users and their data are separated , the communication and networking concepts come into play . Distributed databases re
28、quire 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 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 3 页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 4 formats. Ideally, it would make the mainfra
29、me 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 computer is seen as the master and th
30、e 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 today s personal computers, departmental computers, and distributed processing
31、 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 database applications is to distribu
32、te 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 resources are data in a database ,the c
33、lient/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 large and require fast access .In
34、 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 retrieve files on other computers an
35、d 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 while another user requests the sam
36、e 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 database server is software th
37、at 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 sends the query across the network
38、 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. Sun s Network Filing System(NFS),for example, is used in computer-aided engineering applications to distribute data among the hard disks in a n
39、etwork of Sun workstation. Distributing databases is an evolutionary step because it is logical that data should exist at the 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 4 页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 5 location where they are being used . Departmental computers within a large corporation ,for e
40、xample, should have data reside locally , yet those data 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 diffe
41、rent from the non-distributed database . In this information age, the data server has become the heart of a company. This one piece of software controls the rhythm of most organizations and is used to pump information lifeblood through the arteries of the network. Because of the critical nature of t
42、his application, the data server is also the one of the most popular targets for hackers. If a hacker owns this application, he can cause the companys heart to suffer a fatal arrest. Ironically, although most users are now aware of hackers, they still do not realize how susceptible their database se
43、rvers are to hack attacks. Thus, this article presents a description of the primary methods of attacking database servers (also known as SQL servers) and shows you how to protect yourself from these attacks. You should note this information is not new. Many technical white papers go into great detai
44、l about how to perform SQL attacks, and numerous vulnerabilities have been posted to security lists that describe exactly how certain database applications can be exploited. This article was written for the curious non-SQL experts who do not care to know the details, and as a review to those who do
45、use SQL regularly. What Is a SQL Server? A database application is a program that provides clients with access to data. There are many variations of this type of application, ranging from the expensive enterprise-level Microsoft SQL Server to the free and open source mySQL. Regardless of the flavor,
46、 most database server applications have several things in common. First, database applications use the same general programming language known as SQL, or Structured Query Language. This language, also known as a fourth-level language due to its simplistic syntax, is at the core of how a client commu
47、nicates its requests to the server. Using SQL in its simplest form, a programmer can select, add, update, and delete information in a database. However, SQL can also be used to create and design entire databases, perform various functions on the returned information, and even execute other programs.
48、 To illustrate how SQL can be used, the following is an example of a simple standard SQL query and a more powerful SQL query: Simple: Select * from dbFurniture.tblChair This returns all information in the table tblChair from the database dbFurniture. 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 5
49、页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 6 Complex: EXEC master.xp_cmdshell dir c: This short SQL command returns to the client the list of files and folders under the c: directory of the SQL server. Note that this example uses an extended stored procedure that is exclusive to MS SQL Server. The second functio
50、n that database server applications share is that they all require some form of authenticated connection between client and host. Although the SQL language is fairly easy to use, at least in its basic form, any client that wants to perform queries must first provide some form of credentials that wil
51、l authorize the client; the client also must define the format of the request and response. This connection is defined by several attributes, depending on the relative location of the client and what operating systems are in use. We could spend a whole article discussing various technologies such as
52、 DSN connections, DSN-less connections, RDO, ADO, and more, but these subjects are outside the scope of this article. If you want to learn more about them, a little Googleing will provide you with more than enough information. However, the following is a list of the more common items included in a c
53、onnection request. Database source Request type Database User ID Password Before any connection can be made, the client must define what type of database server it is connecting to. This is handled by a software component that provides the client with the instructions needed to create the request in
54、 the correct format. In addition to the type of database, the request type can be used to further define how the clients request will be handled by the server. Next comes the database name and finally the authentication information. All the connection information is important, but by far the weakest
55、 link is the authentication information or lack thereof. In a properly managed server, each database has its own users with specifically designated permissions that control what type of activity they can perform. For example, a user account would be set up as read only for applications that need to
56、only access information. Another account should be used for inserts or updates, and maybe even a third account would be used for deletes. This type of account control ensures that any compromised account is limited in functionality. Unfortunately, many database programs are set up with null or easy
57、passwords, which leads to successful hack attacks. 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 6 页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 7 译文数据库管理系统介绍数据库也可以称为电子数据库，是专门组织起来的一组数据或信息，其目的是为了便于计算机快速查询及检索。数据库的结构是专门设计的，在各种数据处理操作命令的支持下，可以简化数据的存储，检索， 修改和删除。 数据库可以存储在磁盘，磁带， 光盘或其他辅助存储设备上。数据库由一个或一套文件组成，其中的信息可以分解为记录，每一记
58、录又包含一个或多个字段（或称为域） 。字段是数据存取的基本单位。数据库用于描述实体，其中的一个字段通常表示与实体的某一属性相关的信息。通过关键字以及各种分类（排序）命令，用户可以对多条记录的字段进行查询，重新整理，分组或选择，以实体对某一类数据的检索，也可以生成报表。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
59、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做出回答。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。DBMS 由 3 个主要部分组成： （ 1）存储子系统，用来存储和检索文件中的数据；（2）建模和操作子系统，提供组织数据以及添加，删除，维护，更新数据的方法；（ 3）用户和 DBMS 之间的接口。在提高数据库管理系统的价值和有效性方面正在展现以下一些重要发展趋势；1.管理人员需要最新的信息以做出有效的
60、决策。2.客户需要越来越复杂的信息服务以及更多的有关其订单，发票和账号的当前信息。3.用户发现他们可以使用传统的程序设计语言，在很短的一段时间内用数据库系统开发客户应用程序。4.商业公司发现了信息的战略价值，他们利用数据库系统领先于竞争对手。数据库模型数据库模型描述了在数据库中结构化和操纵数据的方法，模型的结构部分规定了数据如何被描述（例如树，表等）：模型的操纵部分规定了数据添加，删除，显示，维护，打印，查找，选择，排序和更新等操作。分层模型第一个数据库管理系统使用的是分层模型，也就是说，将数据记录排列成树形结构。一些精选学习资料 - - - - - - - - - 名师归纳总结 - - -
61、- - - -第 7 页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 8 记录时根目录，在其他所有记录都有独立的父记录。树形结构的设计反映了数据被使用的顺序，也就是首先访问处于树根位置的记录，接下来是跟下面的记录，等等。分层模型的开发是因为分层关系在商业应用中普遍存在，众所周知，一个组织结构图表就描述了一种分层关系：高层管理人员在最高层，中层管理人员在较低的层次，负责具体事务的雇员在最底层。值得注意的是，在一个严格的分层结构体系中，在每个管理层下可能有多个雇员或多个层次的雇员，但每个雇员只有一个管理者。分层结构数据的典型特征是数据之间的一对多关系。在分层方法中，当数据库建立时，每一
62、关系即被明确地定义。在分层数据库中的每一记录只能包含一个关键字段，任意两个字段之间只能有一种关系。由于数据并不总是遵循这种严格的分层关系，所以这样可能会出现一些问题。关系模型在 1970 年，数据库研究取得了重大突破。E.F.Codd 提出了一种截然不同的数据库管理方法，使用表作为数据结构,称之为关系模型. 关系数据库是使用最广的数据结构,数据被组织成关系表,每个表由称作记录的行和称作字段的列组成。每个记录包含了专用项目的字段值。例如，在一个包含雇员信息的表中，一个记录包含了像一个人姓名和地址这样的字段的值。结构化查询语言 （SQL）是一种在关系型数据库中用于处理数据的查询语言。它是非过程化语
63、言或者说是描述性的，用户只须指定一种类似于英语的描述，用来确定操作，记录或描述记录组合。查询优化器将这种描述翻译为过程执行数据库操作。网状模型网状模型在数据之间通过链接表结构创建关系，子记录可以链接到多个父记录。这种将记录和链接捆绑到一起的方法叫做指针，他是指向一个记录存储位置的存储地址。使用网状方法，一个子记录可以链接到一个关键记录，同时，它本身也可以作为一个关键记录。链接到其他一系列子记录。在早期，网状模型比其他模型更有性能优势；但是在今天，这种优势的特点只有在自动柜员机网络，航空预定系统等大容量和高速处理过程中才是最重要的。分层和网状数据库都是专用程序，如果开发一个新的应用程序，那么在不
64、同的应用程序中保持数据库的一致性是非常困难的。例如开发一个退休金程序，需要访问雇员数据，这一数据同时也被工资单程序访问。虽然数据是相同的，但是也必须建立新的数据库。对象模型最新的数据库管理方法是使用对象模型，记录由被称作对象的实体来描述，可以在对象中存储数据，同时提供方法或程序执行特定的任务。对象模型使用的查询语言与开发数据库程序所使用的面向对象的程序设计语言是相同的，因为没有像SQL 这样简单统一的查询语言，所以会产生一些问题。对象模型相对较新，仅有少数几个面向对象的数据库实例。它引起了人们的关注，因为选择面向对象程序设计语言的开发人精选学习资料 - - - - - - - - - 名师归纳
65、总结 - - - - - - -第 8 页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 9 员希望有一个基于在对象模型基础上的数据库。分布式数据库类似的，分布式数据库指的是数据库的各个部分分别存储在物理上相互分开的计算机上。分布式数据库的一个目的是访问数据信息时不必考虑其他位置。注意，一旦用户和数据分开，通信和网络则开始扮演重要角色。分布式数据库需要部分常驻于大型主机上的软件，这些软件在大型机和个人计算机之间建立桥梁，并解决数据格式不兼容的问题。在理想情况下，大型主机上的数据库看起来像是一个大的信息仓库，而大部分处理则在个人计算机上完成。分布式数据库系统的一个缺点是它们常以主机中心
66、模型为基础，在这种模型中，大型主机看起来好像是雇主，而终端和个人计算机看起来好像是奴隶。但是这种方法也有许多优点：由于数据库的集中控制，前面提到的数据完整性和安全性的问题就迎刃而解了。当今的个人计算机，部门级计算机和分布式处理都需要计算机之间以及应用程序之间在相等或对等的基础上相互通信，在数据库中客户机/服务器模型为分布式数据库提供了框架结构。利用相互连接的计算机上运行的数据库应用程序的一种方法是将程序分解为相互独立的部分。客户端是一个最终用户或通过网络申请资源的计算机程序，服务器是一个运行着的计算机软件，存储着那些通过网络传输的申请。当申请的资源是数据库中的数据时，客户机 /服务器模型则为分
67、布式数据库提供了框架结构。文件服务器指的是一个通过网络提供文件访问的软件，专门的文件服务器是一台被指定为文件服务器的计算机。这是非常有用的，例如，如果文件比较大而且需要快速访问，在这种情况下，一台微型计算机或大型主机将被用作文件服务器。分布式文件服务器将文件分散到不同的计算机上，而不是将它们集中存放到专门的文件服务器上。后一种文件服务器的优点包括在其他计算机上存储和检索文件的能力，并可以在每一台计算机上消除重复文件。然而，一个重要的缺点是每个读写请求需要在网络上传播，在刷新文件时可能出现问题。假设一个用户申请文件中的一个数据并修改它，同时另外一个用户也申请这个数据并修改它，解决这种问题的方法叫
68、做数据锁定，即第一个申请使其他申请处于等待状态，直到完成第一个申请，其他用户可以读取这个数据，但不能修改。数据库服务器是一个通过网络为数据库申请提供服务的软件，例如，假设某个用户在他的个人计算机上输入了一个数据查询命令，如果应用程序按照客户机/服务器模型设计，那么这个人计算机上的查询语言通过网络传送数据库服务器上，当发现数据时发出通知。在工程界也有许多分布式数据库的例子，如SUN 公司的网络文件系统（NFS）被应用到计算机辅助工程应用程序中，将数据分散到由SUN 工作站组成的网络上的不同硬盘之间。分布式数据库是革命性的进步，因为把数据存放在被使用位置上是很合乎常理的。例如一个大公司不同部门之间
69、的计算机，应该将数据存储在本地，然而，当被授权的管理人员需要整理部门数据时，数据应该能够被访问。数据库信息系统软件将保护数据库的安全性和完整性，对用精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 9 页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 10 户而言，分布式数据库和非分布式数据库看起来没有什么差别。在这个信息时代，数据管理服务器已经成为公司的核心。这一个软件的模块控制整个组织的顺利运行就如同人身体动脉使得鲜血在身体中流通顺畅。因为这个所以就要把好身份申请这一关，数据管理服务器也是黑客最为关心的目标之一。如果一旦自己的身份验证被
70、黑客攻克,他将能引起公司的心脏 遭受致命的破坏。虽然大多数的使用者现在知道黑客，但是他们仍然不了解他们的数据库伺候器是多么的易受影响黑客的攻击。因此，这篇文章介绍是如何攻击数据库伺候器(比如SQL 伺候器 ) 和讲述你在受攻击时该如何保护你自己的数据。我们应该注意信息不断更新。许多技术上的空白导致了SQL 在运行时很多细节被攻击的事，而且很多的易受攻击的地方被寄到完全地描述数据库申请能是多么的某开发的安全目录。这个文章对那些好奇的非SQL 专家是书面的不关心知道细节，而且如检讨到那些做的人有规则地使用SQL。一个 SQL 伺候器是做什么的？一个数据库身份验证是一个提供给有权限客户访问数据通道。
71、申请的类型有许多变化,从大企业的微软SQL 伺候器到自由的和开放来源mySQL 排列。不管是什么，大多数的数据库伺候器申请都有共同的一些功能。首先， 数据库申请使用都使用相同的SQL 的语言，或结构查询语言。这些语言， 也属于第四代语言，由于它单纯化的语法，是在一位客户如何向伺候器传达它的请求核心。使用它最简单的形式语言SQL ，一个程序师能选择,增加，更新， 而且在一个数据库中能划分各种数据。然而，SQL 也能用来产生并且设计整个的数据库，运行被送回的数据上的各种不同的功能,甚至运行其他的程序。为了要举例说明SQL 如何使用 ,下列各项是简单标准SQL 的一个例子疑问和一个比较复杂的SQL
72、疑问：简单的：挑选出来的*从 dbFurniture.tblChair 这在来自数据库dbFurniture 的数据库tblChair 中返还的所有数据. 复杂 :管理人员征服。xp_cmdshelldir c 。: 这个短SQL 指令回到客户文件和文件夹的目录在SQL 伺候器的c:directory 之下，注意这个例子使用一个广大的储存对MS SQL 伺候器是独家的程序。第二个功能数据库伺候器申请部份是他们全部需要一些形式的验证进行建立客户和主机之间的连接。虽然SQL 语言基本语法形式使用中很容易。他只要建立一些基础的形式就行了，想要运行任何客户的疑问一定要首先提供一些形式，这将会授权与客户
73、的国书；客户也要有一定的定义请求和回应的格式。这个连接被一些属性定义,仰赖客户的相关位置和什么操作系统是在使用中，我们可以花费整个文章讨论例如DSN 连接，较少的DSN-连接，RDO ，费力和更多的各种不同的技术，但精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 10 页，共 11 页扬州大学计算机专业毕业设计( 外文翻译 ) 11 是这些主题超过了这个文章的范围。如果你想要学习更多有关他们，一些Googleing 将会提供更充足的数据给你。然而，下列各项是被包含在关系中一些连接请求的一连串的比较通常的项目。数据库来源请求类型数据库使用者身份证密码
74、任何的连接在连接之前，客户要连接到什么类型的伺候器。这被一个提供被需要在正确的格式中产生请求的指令给客户的软件成份处理。除了数据库的类型，请求类型能用来比较进一步定义客户的请求将会如何被伺候器处理。下一个来数据库名字和最后证明数据。所有的连接信息都很重要，但是显然最弱的联编是关于证明数据或缺乏。在适当地处理了伺候器。每个数据库明确地用有它的自己使用者指定了控制他们能运行什麽类型的活动许可。举例来说，一个使用者帐户会是建立如申请所只有读哪一对唯一的通路数据需要。另外的一个帐户应该作为插入物或更新，而且也许甚至一个第三帐户会是使用过的因为划除。帐户控制的这个类型确定那个任何的被妥协处理的帐户在功能性中被限制。不幸地，许多数据库计画是建立由于无效力的或容易的密码，导致成功的攻击。Modern Database Management7 th EditionJeffrey A. Hoffer, Mary B. Prescott,Fred R. McFadden精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 11 页，共 11 页
