2022年外文翻译原文及译文V实用 .pdf

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1、外文翻译原文及译文学院计算机学院专业计算机科学与技术班级14010105 学号2011040101218 姓名彭博文指导教师王丹负责教师沈阳航空航天大学2015 年 6 月名师资料总结-精品资料欢迎下载-名师精心整理-第 1 页，共 9 页 -沈阳航空航天大学毕业设计（论文）外文翻译译文1 SQLITE DISTINCTIVE FEATURES This article highlights some of the characteristics of SQLite that are unusual and which make SQLite different from many other

2、 SQL database engines.Zero-ConfigurationSQLite does not need to be installed before it is used.There is no setup procedure.There is no server process that needs to be started,stopped,or configured.There is no need for an administrator to create a new database instance or assign access permissions to

3、 users.SQLite uses no configuration files.Nothing needs to be done to tell the system that SQLite is running.No actions are required to recover after a system crash or power failure.There is nothing to troubleshoot.Other more familiar database engines run great once you get them going.But doing the

4、initial installation and configuration can be intimidatingly complex.ServerlessMost SQL database engines are implemented as a separate server process.Programs that want to access the database communicate with the server using some kind of interprocess communication(typically TCP/IP)to send requests

5、to the server and to receive back results.SQLite does not work this way.With SQLite,the process that wants to access the database reads and writes directly from the database files on disk.There is no intermediary server process.There are advantages and disadvantages to being serverless.The main adva

6、ntage is that there is no separate server process to install,setup,configure,initialize,manage,and troubleshoot.This is one reason why SQLite is a zero-configuration database engine.Programs that use SQLite require no administrative support for setting up the database engine before they are run.Any

7、program that is able to access the disk is able to use an SQLite database.On the other hand,a database engine that uses a server can provide better protection from bugs in the client application-stray pointers in a client cannot corrupt memory on the server.And because a server is a single persisten

8、t process,it is able control database access with more precision,allowing for finer grain locking and better concurrency.Most SQL database engines are client/server based.Of those that are serverless,SQLite is the only one that this author knows of that allows multiple applications to access the sam

9、e database at the same time.Single Database FileAn SQLite database is a single ordinary disk file that can be located anywhere in the directory hierarchy.If SQLite can read the disk file then it 名师资料总结-精品资料欢迎下载-名师精心整理-第 2 页，共 9 页 -沈阳航空航天大学毕业设计（论文）外文翻译译文2 can read anything in the database.If the disk

10、 file and its directory are writable,then SQLite can change anything in the database.Database files can easily be copied onto a USB memory stick or emailed for sharing.Other SQL database engines tend to store data as a large collection of files.Often these files are in a standard location that only

11、the database engine itself can access.This makes the data more secure,but also makes it harder to access.Some SQL database engines provide the option of writing directly to disk and bypassing the filesystem all together.This provides added performance,but at the cost of considerable setup and mainte

12、nance complexity.Stable Cross-Platform Database FileThe SQLite file format is cross-platform.A database file written on one machine can be copied to and used on a different machine with a different architecture.Big-endian or little-endian,32-bit or 64-bit does not matter.All machines use the same fi

13、le format.Furthermore,the developers have pledged to keep the file format stable and backwards compatible,so newer versions of SQLite can read and write older database files.Most other SQL database engines require you to dump and restore the database when moving from one platform to another and ofte

14、n when upgrading to a newer version of the software.CompactWhen optimized for size,the whole SQLite library with everything enabled is less than 500KiB in size(as measured on an ix86 using the size utility from the GNU compiler suite.)Unneeded features can be disabled at compile-time to further redu

15、ce the size of the library to under 300KiB if desired.Most other SQL database engines are much larger than this.IBM boasts that its recently released CloudScape database engine is only a 2MiB jar file-an order of magnitude larger than SQLite even after it is compressed!Firebird boasts that its clien

16、t-side library is only 350KiB.Thats as big as SQLite and does not even contain the database engine.The Berkeley DB library from Oracle is 450KiB and it omits SQL support,providing the programmer with only simple key/value pairs.Manifest typingMost SQL database engines use static typing.A datatype is

17、 associated with each column in a table and only values of that particular datatype are allowed to be stored in that column.SQLite relaxes this restriction by using manifest typing.In manifest typing,the datatype is a property of the value itself,not of the column in which the value is stored.SQLite

18、 thus allows the user to store any value of any datatype into any column regardless of the declared type of that column.(There are some exceptions to this rule:An INTEGER PRIMARY KEY column may only store integers.And SQLite attempts to coerce values into the declared datatype of the column when it

19、can.)名师资料总结-精品资料欢迎下载-名师精心整理-第 3 页，共 9 页 -沈阳航空航天大学毕业设计（论文）外文翻译译文3 As far as we can tell,the SQL language specification allows the use of manifest typing.Nevertheless,most other SQL database engines are statically typed and so some people feel that the use of manifest typing is a bug in SQLite.But the

20、 authors of SQLite feel very strongly that this is a feature.The use of manifest typing in SQLite is a deliberate design decision which has proven in practice to make SQLite more reliable and easier to use,especially when used in combination with dynamically typed programming languages such as Tcl a

21、nd Python.Variable-length recordsMost other SQL database engines allocated a fixed amount of disk space for each row in most tables.They play special tricks for handling BLOBs and CLOBs which can be of wildly varying length.But for most tables,if you declare a column to be a VARCHAR(100)then the dat

22、abase engine will allocate 100 bytes of disk space regardless of how much information you actually store in that column.SQLite,in contrast,use only the amount of disk space actually needed to store the information in a row.If you store a single character in a V ARCHAR(100)column,then only a single b

23、yte of disk space is consumed.(Actually two bytes-there is some overhead at the beginning of each column to record its datatype and length.)The use of variable-length records by SQLite has a number of advantages.It results in smaller database files,obviously.It also makes the database run faster,sin

24、ce there is less information to move to and from disk.And,the use of variable-length records makes it possible for SQLite to employ manifest typing instead of static typing.Readable source codeThe source code to SQLite is designed to be readable and accessible to the average programmer.All procedure

25、s and data structures and many automatic variables are carefully commented with useful information about what they do.Boilerplate commenting is omitted.SQL statements compile into virtual machine codeEvery SQL database engine compiles each SQL statement into some kind of internal data structure whic

26、h is then used to carry out the work of the statement.But in most SQL engines that internal data structure is a complex web of interlinked structures and objects.In SQLite,the compiled form of statements is a short program in a machine-language like representation.Users of the database can view this

27、 virtual machine language by prepending the EXPLAIN keyword to a query.The use of a virtual machine in SQLite has been a great benefit to the librarys development.The virtual machine provides a crisp,well-defined junction between the front-end of SQLite(the part that parses SQL statements and genera

28、tes virtual machine code)and the back-end(the part 名师资料总结-精品资料欢迎下载-名师精心整理-第 4 页，共 9 页 -沈阳航空航天大学毕业设计（论文）外文翻译译文4 that executes the virtual machine code and computes a result.)The virtual machine allows the developers to see clearly and in an easily readable form what SQLite is trying to do with each s

29、tatement it compiles,which is a tremendous help in debugging.Depending on how it is compiled,SQLite also has the capability of tracing the execution of the virtual machine-printing each virtual machine instruction and its result as it executes.Public domainThe source code for SQLite is in the public

30、 domain.No claim of copyright is made on any part of the core source code.(The documentation and test code is a different matter-some sections of documentation and test logic are governed by open-source licenses.)All contributors to the SQLite core software have signed affidavits specifically disavo

31、wing any copyright interest in the code.This means that anybody is able to legally do anything they want with the SQLite source code.There are other SQL database engines with liberal licenses that allow the code to be broadly and freely used.But those other engines are still governed by copyright la

32、w.SQLite is different in that copyright law simply does not apply.The source code files for other SQL database engines typically begin with a comment describing your license rights to view and copy that file.The SQLite source code contains no license since it is not governed by copyright.Instead of

33、a license,the SQLite source code offers a blessing:May you do good and not evil May you find forgiveness for yourself and forgive others May you share freely,never taking more than you give.SQL language extensionsSQLite provides a number of enhancements to the SQL language not normally found in othe

34、r database engines.The EXPLAIN keyword and manifest typing have already been mentioned above.SQLite also provides statements such as REPLACE and the ON CONFLICT clause that allow for added control over the resolution of constraint conflicts.SQLite supports ATTACH and DETACH commands that allow multi

35、ple independent databases to be used together in the same query.And SQLite defines APIs that allows the user to add new SQL functions and collating sequences.名师资料总结-精品资料欢迎下载-名师精心整理-第 5 页，共 9 页 -沈阳航空航天大学毕业设计（论文）外文翻译译文5 SQLITE明显的特征这篇文章突出了一些的SQLite 是不寻常的，体现SQLite 不同于许多其他的SQL数据库引擎的特点。零配置SQLite 不需要被“安装”在

36、使用前。有没有“设置”程序。不存在需要被启动的服务器上的过程中，停止，或配置。有没有需要管理员来创建一个新的数据库实例或分配访问权限的用户。SQLite 的不使用配置文件。没有什么需要做的来告诉SQLite 的运行系统。任何行动都需要在系统崩溃或电源故障后的恢复。有什么解决。其他更熟悉的数据库引擎运行伟大的，一旦你让他们去。但这样做的初始安装和配置可以intimidatingly复杂。无服务器大多数 SQL数据库引擎被实现为一个独立的服务器进程。该要访问的数据库程序，使用某种进程间通信（通常是TCP/IP）的发送请求到服务器并接收返回的结果与服务器通信。SQLite 不以这种方式工作。使用 S

37、QLite，想要访问的数据库直接读写从数据库磁盘上的文件的过程。不存在中介服务器进程。有优点和缺点是无服务器。其主要优点是，有没有独立的服务器进程来安装，安装，配置，初始化，管理和故障排除。这是原因之一，SQLite 是一个“零配置”数据库引擎。使用SQLite 的计划需要来设置数据库引擎，他们正在运行之前没有行政支持。任何程序，它是能够访问磁盘能够使用SQLite 数据库。在另一方面，使用服务器的数据库引擎可以提供从错误的客户端应用程序更好的保护-在客户流浪指针可以在服务器上的未损坏内存。而由于服务器是一个单一的持久的过程，它是更精确的控制能力的数据库访问，允许更细的颗粒锁定和更好的并发。大

38、多数SQL数据库引擎是基于客户/服务器。那些无服务器的，SQLite 是这作者知道的，允许多个应用同时访问同一数据库中的唯一的一个。单个数据库文件SQLite 数据库是可以位于目录层次结构的任何地方一个普通的磁盘文件。如果 SQLite 的可以读取磁盘文件，那么它可以读取数据库中的任何内容。如果磁盘文件和它的目录是可写的，则SQLite 的可以改变数据库中的任何内容。数据库文件可以很容易地复制到一个USB记忆棒或通过电子邮件共享。名师资料总结-精品资料欢迎下载-名师精心整理-第 6 页，共 9 页 -沈阳航空航天大学毕业设计（论文）外文翻译译文6 其它 SQL数据库引擎往往数据存储为一个大的文

39、件集合。通常，这些文件是在只有数据库引擎本身可访问的标准位置。这使得数据更安全，但也使得它更难获得。有些 SQL数据库引擎提供直接写入到磁盘，并绕过了文件系统的所有共同的选择。这提供了额外的性能，但在具有相当的设置和维护的复杂性的费用。稳定的跨平台数据库文件SQLite 的文件格式是跨平台的。写在一台机器上的数据库文件可以被复制并使用不同的机器上有不同的架构。大端或小端，32 位或 64位无所谓。所有的机器使用相同的文件格式。此外，开发商已承诺保持文件格式稳定，向下兼容，所以新版本的SQLite 可以读取和写入旧的数据库文件。大多数其他的 SQL数据库引擎需要你从一个平台升级到软件的新版本时，

40、移动到另一个时经常转储和恢复数据库。紧凑在为大小进行了优化，整个SQLite 库的一切是启用 不到 500KiB 的大小（如测量使用的“大小”工具从GNU 编译器套件的 IX86）不必要的功能可以在编译时被禁用，以进一步降低300KiB 下库的大小，如果需要的。大多数其他 SQL数据库引擎比这大得多。IBM拥有其最近发布的Cloudscape 数据库引擎是“唯一”的一个2MiB jar文件-要比较大的 SQLite 被压缩，即使一个数量级！火鸟拥有其客户端库仅350KiB。这是大如 SQLite 的甚至不包含数据库引擎。从Oracle Berkeley DB库是 450KiB，它忽略了 SQL

41、的支持，提供了程序员，只有简单的键/值对。清单打字大多数 SQL数据库引擎使用静态类型。一个数据类型与表和该特定数据类型的唯一值的各列相关联的允许被存储在该列。SQLite 的放宽这种限制使用清单打字。清单中打字，数据类型为值本身的性质，而不是列的，其中的值被存储。的SQLite 从而允许用户无论来存储列的声明类型的任何数据类型的任何值到任何列。（有一些例外情况：一个 INTEGER PRIMARY KEY 列仅存储整数和 SQLite 试图强迫值代入列的声明数据类型时，它可以。）据我们所知道的，SQL语言规范允许使用清单打字。然而，大多数其它 SQL数据库引擎都是静态类型，因此有些人觉得使用

42、清单打字是 SQLite 中的一个错误。但 SQLite 的的作者非常强烈地认为，这是一个特点。SQLite 中使用清单打字是一个深思熟虑的设计决定它已被证明在实践中，使SQLite 的更可靠，更易于使用，结合使用动态类型的编程语言如TCL和 Python 时尤其如此。变长记录名师资料总结-精品资料欢迎下载-名师精心整理-第 7 页，共 9 页 -沈阳航空航天大学毕业设计（论文）外文翻译译文7 大多数其它 SQL数据库引擎分配的磁盘空间量固定在大多数表的每一行。他们发挥特殊的技巧来处理BLOB 和 CLOB 它可以是疯狂长短不一。但对于大多数的表，如果你声明一列是一个VARCHAR（100），

43、则数据库引擎将分配 100字节的磁盘空间，无论你实际上有多少信息存储在该列中。SQLite 的，与此相反，使用的实际需要来存储在一行中的信息的磁盘空间仅量。如果在一个VARCHAR（100）列中存储单个字符，磁盘空间那么只有一个字节被消耗。（实际上两个字节-有一些开销在每列的开头，记录其数据类型和长度。）通过SQLite 的使用可变长度记录有许多优点。它导致较小的数据库文件，效果显着。这也使得数据库运行得更快，因为有较少的移动和从磁盘信息。并且，采用可变长度记录可以使 SQLite 的采用明显的打字，而不是静态类型。可读的源代码源代码的 SQLite 被设计成可读和可对普通程序员。所有程序和数

44、据结构和许多自动变量都经过精心注释与他们做什么有用的信息。样板评论被省略。SQL语句编译成虚拟机代码每个 SQL数据库引擎编译每个SQL语句转换成某种内部数据结构，然后用于进行发言的工作。但在大多数的 SQL引擎内部数据结构是相通的结构和对象的复杂网络。SQLite 中，语句的编译形式是在一个机器语言类似表示的短节目。该数据库的用户可以查看此虚拟机器语言通过预先的 EXPLAIN 关键字查询。SQLite 中使用虚拟机一直是大有裨益图书馆的发展。虚拟机提供了一个清晰的，明确定义的SQLite 和后端（即执行该虚拟机的代码，并计算结果的一部分（即解析 SQL语句，并生成虚拟机器代码的一部分）的前

45、端之间的接合。）虚拟机可以让开发者看到清晰和易读的形式是什么SQLite 是尝试与每个语句汇编，这是在调试一个巨大的帮助。取决于它是如何编译时，SQLite 还具有追踪虚拟机的执行的能力 -在执行打印每个虚拟机指令和其结果。公共领域SQLite 的源代码是在公共领域。著作权的没有提出索赔的任何部分的核心的源代码。（文档和测试代码是另一回事-文档和测试逻辑部分路段由开源许可证的管辖）所有贡献者SQLite 的核心软件已签署宣誓书专门 disavowing 代码中的任何版权利益。这意味着，任何人都可以合法地做任何他们想要的SQLite 的源代码。还有其他的SQL数据库引擎与自由的许可，允许代码是广

46、泛的和自由使用。但是，这些其他引擎都受版权法依然制约。SQLite 是不同之处在于版权法根本不适用。名师资料总结-精品资料欢迎下载-名师精心整理-第 8 页，共 9 页 -沈阳航空航天大学毕业设计（论文）外文翻译译文8 源代码文件为其它SQL数据库引擎通常以一个注释，描述你的许可权限，以查看和复制文件。SQLite 的源代码，不包含任何许可证，因为它不是受版权支配。牌照相反，SQLite 的源代码提供了祝福：也许你做的好事，而不是坏事。愿你找到原谅自己，原谅别人，你可以自由地共享，根本不把超过你的付出。SQL语言扩展SQLite 的提供了许多增强功能不正常的其他数据库引擎中的SQL语言。EXPLAIN关键字和打字表现上面已经提及。SQLite 的也提供了诸如语句 REPLACE 和 ON CONFLICT 子句允许过约束冲突的解决增加的控制。SQLite 支持 ATTACH 和 DETACH 命令允许一起使用在同一个查询多个独立的数据库。和 SQLite 定义的 API，允许用户添加新的SQL函数和整理顺序。名师资料总结-精品资料欢迎下载-名师精心整理-第 9 页，共 9 页 -