﻿<?xml version="1.0" encoding="utf-8" standalone="yes"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:trackback="http://madskills.com/public/xml/rss/module/trackback/" xmlns:wfw="http://wellformedweb.org/CommentAPI/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/"><channel><title>C++博客-twzheng's cppblog-随笔分类-数据库</title><link>http://www.cppblog.com/twzheng/category/5414.html</link><description>『站在风口浪尖紧握住鼠标旋转！』</description><language>zh-cn</language><lastBuildDate>Sat, 21 Mar 2009 21:32:13 GMT</lastBuildDate><pubDate>Sat, 21 Mar 2009 21:32:13 GMT</pubDate><ttl>60</ttl><item><title>如何查看SQLSERVER的版本</title><link>http://www.cppblog.com/twzheng/archive/2009/03/22/77455.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Sat, 21 Mar 2009 17:48:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2009/03/22/77455.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/77455.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2009/03/22/77455.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/77455.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/77455.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 8.00.194 v2000<br>8.00.384 v2000 SP1<br>8.00.534 v2000 SP2<br>8.00.760 v2000 SP3<br>8.00.2039 v2000 SP4<br><br>9.00.1399.06 v2005<br>9.00.2047.00 V2005 SP1&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2009/03/22/77455.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/77455.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2009-03-22 01:48 <a href="http://www.cppblog.com/twzheng/archive/2009/03/22/77455.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>c# 本地和远程连接数据库SQL和ACCESS的字符串</title><link>http://www.cppblog.com/twzheng/archive/2009/03/22/77451.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Sat, 21 Mar 2009 16:00:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2009/03/22/77451.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/77451.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2009/03/22/77451.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/77451.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/77451.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 5 检查服务器是否在1433端口侦听。如果服务器没有在tcp连接的1433端口侦听，则是连接不上的。检 <br><br>          查方法是在服务器的dos或命令行下面输入 <br>          netstat -a -n 或者是netstat -an，在结果列表里看是否有类似                  tcp   127.0.0.1 1433   listening <br><br>          的项。如果没有，则通常需要给sql server         2000打上至少sp3的补丁。其实在服务器端启动查询分<br><br>          析器，输入 select @@version 执行后可以看到版本号，版本号在8.0.2039以下的都需要打补丁。<br>          如果以上都没问题，这时你再做telnet 服务器ip 1433 测试，将会看到屏幕一 闪之后光标在左上<br><br>          角不停闪动。恭喜你，你马上可以开始在企业管理器或查询分析 器连接了。<br>&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2009/03/22/77451.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/77451.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2009-03-22 00:00 <a href="http://www.cppblog.com/twzheng/archive/2009/03/22/77451.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>实战剖析三层架构1 </title><link>http://www.cppblog.com/twzheng/archive/2008/11/16/67075.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Sun, 16 Nov 2008 14:59:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2008/11/16/67075.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/67075.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2008/11/16/67075.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/67075.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/67075.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 引言：本文不是从理论的角度来探讨三层架构，而是用一个示例来介绍如何建设一个三层架构的项目，并说明项目中各个文件所处的层次与作用。写本文的目的，不是为了说明自己的这个方法有多对，别人的肯定不对，而是希望给那些初学三层架构却不知从何入手的朋友提供一点帮助。因为网上的文章，大多是注重理论的介绍，而忽略了具体的实践应用，或者有示例但讲得不透彻。导致看了之后，理论上又学习了一遍，但还是不知道代码怎么写。所以想从这个方面入手写一下，让从来没做过三层架构的初学者也能照猫画虎，写出代码来。文章表述的是笔者个人对三层架构的认识，肯定有许多不足的地方，欢迎大家指正，小弟也会根据反馈来修改这篇文章。文中的代码是伪代码，仅用来阐明思路。&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2008/11/16/67075.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/67075.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2008-11-16 22:59 <a href="http://www.cppblog.com/twzheng/archive/2008/11/16/67075.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>使用SQL语句创建数据库</title><link>http://www.cppblog.com/twzheng/archive/2008/07/07/55508.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Mon, 07 Jul 2008 01:25:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2008/07/07/55508.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/55508.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2008/07/07/55508.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/55508.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/55508.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 用CREATE DATABASE创建数据库的语法格式：<br>    CREATE DATABASE database_name   /*指定数据库名*/<br>    [ON子句]                         /*指定数据库文件和文件组属性*/<br>    [LOG子句]                         /*指定日志文件属性*/&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2008/07/07/55508.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/55508.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2008-07-07 09:25 <a href="http://www.cppblog.com/twzheng/archive/2008/07/07/55508.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>sql server 2000 函数大全</title><link>http://www.cppblog.com/twzheng/archive/2008/05/31/51668.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Sat, 31 May 2008 00:54:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2008/05/31/51668.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/51668.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2008/05/31/51668.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/51668.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/51668.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: &nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2008/05/31/51668.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/51668.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2008-05-31 08:54 <a href="http://www.cppblog.com/twzheng/archive/2008/05/31/51668.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>SQL Server与Excel数据互导</title><link>http://www.cppblog.com/twzheng/archive/2008/03/20/44953.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Thu, 20 Mar 2008 07:32:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2008/03/20/44953.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/44953.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2008/03/20/44953.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/44953.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/44953.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 　　--如果接受数据导入的表已经存在<br><br>　　insert into 表 select * from<br><br>　　OPENROWSET('MICROSOFT.JET.OLEDB.4.0'<br><br>　　,'Excel 5.0;HDR=YES;DATABASE=c:test.xls',sheet1$)<br><br>　　--如果导入数据并生成表<br><br>　　select * into 表 from<br><br>　　OPENROWSET('MICROSOFT.JET.OLEDB.4.0'<br><br>　　,'Excel 5.0;HDR=YES;DATABASE=c:test.xls',sheet1$)<br>&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2008/03/20/44953.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/44953.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2008-03-20 15:32 <a href="http://www.cppblog.com/twzheng/archive/2008/03/20/44953.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>定位修改删除游标</title><link>http://www.cppblog.com/twzheng/archive/2008/03/07/43905.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Fri, 07 Mar 2008 09:47:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2008/03/07/43905.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/43905.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2008/03/07/43905.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/43905.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/43905.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 　　通常情况下我们用游标来从基础表中检索数据，以实现对数据的行处理。但在某些情况下，我们也常要修改游标中的数据，即进行定位更新或删除游标所包含的数据。所以必须执行另外的更新或删除命令，并在WHERE 子句中重新给定条件才能修改到该行数据。但是如果在声明游标时使用了FOR UPDATE 语句，那么就可以在UPDATE 或DELETE命令中以WHERE CURRENT OF 关键字直接修改或删除当前游标中所存储的数据，而不必使用WHERE 子句重新给出指定条件。当改变游标中数据时，这种变化会自动地影响到游标的基础表。但是如果在声明游标时选择了INSENSITIVE 选项时，该游标中的数据不能被修改，具体含义请参看声明游标一节中对INSENSITIVE 选项的详细解释。&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2008/03/07/43905.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/43905.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2008-03-07 17:47 <a href="http://www.cppblog.com/twzheng/archive/2008/03/07/43905.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>数据库备份与还原处理</title><link>http://www.cppblog.com/twzheng/archive/2008/01/19/41475.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Sat, 19 Jan 2008 09:14:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2008/01/19/41475.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/41475.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2008/01/19/41475.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/41475.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/41475.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 利用T-SQL语句,实现数据库的备份与还原的功能<br><br>体现了SQL Server中的四个知识点： <br>1．   获取SQL Server服务器上的默认目录 <br>2．   备份SQL语句的使用<br>3．   恢复SQL语句的使用，同时考虑了强制恢复时关闭其他用户进程的处理 <br>4．   作业创建SQL语句的使用&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2008/01/19/41475.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/41475.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2008-01-19 17:14 <a href="http://www.cppblog.com/twzheng/archive/2008/01/19/41475.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>SQL Server 数据库事务处理详解</title><link>http://www.cppblog.com/twzheng/archive/2007/12/19/38963.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Tue, 18 Dec 2007 16:21:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2007/12/19/38963.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/38963.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2007/12/19/38963.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/38963.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/38963.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 事务定义：<br>事务是单个的工作单元。如果某一事务成功，则在该事务中进行的所有数据更改均会提交，成为数据库中的永久组成部分。如果事务遇到错误且必须取消或回滚，则所有数据更改均被清除。<br><br>事务三种运行模式：<br>自动提交事务每条单独的语句都是一个事务。显式事务每个事务均以 BEGIN TRANSACTION 语句显式开始，以 COMMIT 或 ROLLBACK 语句显式结束。隐性事务在前一个事务完成时新事务隐式启动，但每个事务仍以 COMMIT 或 ROLLBACK 语句显式完成。<br>。。。。。。<br>&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2007/12/19/38963.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/38963.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2007-12-19 00:21 <a href="http://www.cppblog.com/twzheng/archive/2007/12/19/38963.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>使用ADO.NET配置SQL Server事务处理</title><link>http://www.cppblog.com/twzheng/archive/2007/12/19/38962.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Tue, 18 Dec 2007 16:06:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2007/12/19/38962.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/38962.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2007/12/19/38962.html#Feedback</comments><slash:comments>1</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/38962.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/38962.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要:         ADO.NET提供了处理后台数据所需要的一切功能，并且使用起来就如同从一张表格中读取一个数据那样简单。事务处理（transaction）允许你把数据库操作归为一组，由此来保证所有的操作都能够执行。因为一旦其中的一项操作执行失败，则整个事务处理都会失败。现在让我们来看看在.NET Framework下是如何使用事务处理的。<br>&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2007/12/19/38962.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/38962.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2007-12-19 00:06 <a href="http://www.cppblog.com/twzheng/archive/2007/12/19/38962.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>SQL常用字符串函数</title><link>http://www.cppblog.com/twzheng/archive/2007/12/05/37891.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Wed, 05 Dec 2007 15:49:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2007/12/05/37891.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/37891.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2007/12/05/37891.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/37891.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/37891.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 一、字符转换函数<br>二、去空格函数<br>三、取子串函数<br>四、字符串比较函数<br>五、字符串操作函数<br>六、数据类型转换函数<br>七、日期函数&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2007/12/05/37891.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/37891.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2007-12-05 23:49 <a href="http://www.cppblog.com/twzheng/archive/2007/12/05/37891.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>SQL Server触发器问题总结</title><link>http://www.cppblog.com/twzheng/archive/2007/12/04/37762.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Tue, 04 Dec 2007 03:47:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2007/12/04/37762.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/37762.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2007/12/04/37762.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/37762.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/37762.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 递归触发器   <br>  递归触发器资料   <br>  http://topic.csdn.net/t/20050524/07/4030396.html   <br>  递归最大层数的限制   <br>  http://topic.csdn.net/t/20041125/23/3589401.html   <br>  如何禁用递归调用触发器   <br>  http://topic.csdn.net/t/20041116/15/3557957.html   <br>  http://topic.csdn.net/t/20050426/16/3968278.html   <br>    <br>  暂时禁用触发器   <br>  http://topic.csdn.net/t/20041207/17/3623631.html   <br>  http://topic.csdn.net/t/20041111/09/3542063.html   <br>  http://topic.csdn.net/t/20050329/15/3891227.html   <b&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2007/12/04/37762.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/37762.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2007-12-04 11:47 <a href="http://www.cppblog.com/twzheng/archive/2007/12/04/37762.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>SQL中char、varchar、text和nchar、nvarchar、ntext的区别</title><link>http://www.cppblog.com/twzheng/archive/2007/11/29/37498.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Thu, 29 Nov 2007 07:10:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2007/11/29/37498.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/37498.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2007/11/29/37498.html#Feedback</comments><slash:comments>1</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/37498.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/37498.html</trackback:ping><description><![CDATA[<div class=cnt><strong style="FONT-SIZE: 18pt">SQL中char、varchar、text和nchar、nvarchar、ntext的区别</strong><br><br><br>&nbsp;&nbsp;&nbsp;&nbsp; 1、CHAR。CHAR存储定长数据很方便，CHAR字段上的索引效率级高，比如定义char(10)，那么不论你存储的数据是否达到了10个字节，都要占去10个字节的空间。<br>&nbsp;&nbsp;&nbsp;&nbsp; 2、VARCHAR。存储变长数据，但存储效率没有CHAR高。如果一个字段可能的值是不固定长度的，我们只知道它不可能超过10个字符，把它定义为 VARCHAR(10)是最合算的。VARCHAR类型的实际长度是它的值的实际长度+1。为什么&#8220;+1&#8221;呢？这一个字节用于保存实际使用了多大的长度。<br>&nbsp;&nbsp;&nbsp; 从空间上考虑，用varchar合适；从效率上考虑，用char合适，关键是根据实际情况找到权衡点。<br>&nbsp;&nbsp;&nbsp; 3、TEXT。text存储可变长度的非Unicode数据，最大长度为2^31-1(2,147,483,647)个字符。<br>&nbsp;&nbsp;&nbsp;&nbsp; 4、NCHAR、NVARCHAR、NTEXT。这三种从名字上看比前面三种多了个&#8220;N&#8221;。它表示存储的是Unicode数据类型的字符。我们知道字符中，英文字符只需要一个字节存储就足够了，但汉字众多，需要两个字节存储，英文与汉字同时存在时容易造成混乱，Unicode字符集就是为了解决字符集这种不兼容的问题而产生的，它所有的字符都用两个字节表示，即英文字符也是用两个字节表示。nchar、nvarchar的长度是在1到4000之间。和char、varchar比较起来，nchar、nvarchar则最多存储4000个字符，不论是英文还是汉字；而char、varchar最多能存储8000个英文，4000个汉字。可以看出使用nchar、nvarchar数据类型时不用担心输入的字符是英文还是汉字，较为方便，但在存储英文时数量上有些损失。<br>&nbsp;&nbsp;&nbsp;&nbsp; 所以一般来说，如果含有中文字符，用nchar/nvarchar，如果纯英文和数字，用char/varchar。</div>
<img src ="http://www.cppblog.com/twzheng/aggbug/37498.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2007-11-29 15:10 <a href="http://www.cppblog.com/twzheng/archive/2007/11/29/37498.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item><item><title>类型化数据集与非类型化数据集</title><link>http://www.cppblog.com/twzheng/archive/2007/11/26/37348.html</link><dc:creator>谭文政</dc:creator><author>谭文政</author><pubDate>Mon, 26 Nov 2007 14:59:00 GMT</pubDate><guid>http://www.cppblog.com/twzheng/archive/2007/11/26/37348.html</guid><wfw:comment>http://www.cppblog.com/twzheng/comments/37348.html</wfw:comment><comments>http://www.cppblog.com/twzheng/archive/2007/11/26/37348.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/twzheng/comments/commentRss/37348.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/twzheng/services/trackbacks/37348.html</trackback:ping><description><![CDATA[&nbsp;&nbsp;&nbsp;&nbsp; 摘要: 类型化数据集先是从基类 DataSet 派生，然后使用“数据集设计器”中的信息（存储在 .xsd 文件中）生成一个新的强类型数据集类。架构中的信息（表、列等）被作为一组第一类对象和属性生成并编译为此新数据集类。由于类型化数据集继承自基 DataSet 类，因此类型化类具有 DataSet 类的所有功能，可以与采用 DataSet 类的实例作为参数的方法一起使用。&nbsp;&nbsp;<a href='http://www.cppblog.com/twzheng/archive/2007/11/26/37348.html'>阅读全文</a><img src ="http://www.cppblog.com/twzheng/aggbug/37348.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/twzheng/" target="_blank">谭文政</a> 2007-11-26 22:59 <a href="http://www.cppblog.com/twzheng/archive/2007/11/26/37348.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item></channel></rss>