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人们在使用SQL时往往会陷入一个误区,即太关注于所得的结果是否正确,而忽略了不同的实现方法之间可能存在的 性能差异,这种性能差异在大型的或是复杂的数据库环境中(...
人们在使用SQL时往往会陷入一个误区,即太关注于所得的结果是否正确,而忽略了不同的实现方法之间可能存在的 性能差异,这种性能差异在大型的或是复杂的数据库环境中(如联机事务处理OLTP或决策支持系统DSS)中表现得尤为明 显。笔者在工作实践中发现,不良的SQL往往来自于不恰当的索引设计、不充份的连接条件和不可优化的where子句。在对 它们进行适当的优化后,其运行速度有了明显地提高!下面我将从这三个方面分别进行总结:-people in the use of SQL often fall into the trap, that is too focused on the findings is correct, and ignore a different method may exist between the performance differences, these differences in large or complex database environment (such as online transaction processing or decision support OLTP system DSS) has become even more obvious. In practice I found that the poor tend to SQL from inappropriate design of the index, not fully connected and non-optimal conditions where the phrase. On their proper optimization, and their operating speed has been improved! Now I will be three aspects of this summary :
- 2022-07-14 22:31:11下载
- 积分:1
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此文件实现了在VC++中动态创建对话框的功能,源文件包括很多函数说明了采用何种方法实现动态的创建对话框。此程序来自《电脑编程技巧与维护》。...
此文件实现了在VC++中动态创建对话框的功能,源文件包括很多函数说明了采用何种方法实现动态的创建对话框。此程序来自《电脑编程技巧与维护》。-achieved in VC dynamic dialog creation functions, including many of the source documents note the function method used to create dynamic dialog. This program from the "computer programming skills and maintenance."
- 2022-01-25 20:29:30下载
- 积分:1
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简单易懂屏幕捕捉程序,改变静态框背景色,图标的Listcontrol配合属性页
简单易懂屏幕捕捉程序,改变静态框背景色,图标的Listcontrol配合属性页,基本控件的使用
- 2022-03-03 07:57:48下载
- 积分:1
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MFC库,VC++开发环境,实现XP风格的tab control,可改变tab的位置,上下左右...
MFC库,VC++开发环境,实现XP风格的tab control,可改变tab的位置,上下左右-MFC Library, VC++ Development environment, realize XP style tab control, can change the tab position from top to bottom around
- 2023-08-15 07:25:02下载
- 积分:1
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Data structure to achieve the prim tree, friends who are interested can look at.
数据结构里的prim树的实现,有兴趣的朋友可以看看。-Data structure to achieve the prim tree, friends who are interested can look at.
- 2022-04-28 12:37:06下载
- 积分:1
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Winform可视化打印模板设计
Winform可视化打印模板设计
- 2023-06-01 13:15:02下载
- 积分:1
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qt 做的文本编辑器
qt creator 做的文本编辑器,有具体菜单栏,状态栏。可以查看或编写文档。适合初学者!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
- 2022-07-23 22:29:50下载
- 积分:1
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VC interface display, split the window and realizing the complexity of the windo...
VC界面显示的,分割窗口,实现窗口复杂化-VC interface display, split the window and realizing the complexity of the window
- 2022-03-16 07:08:58下载
- 积分:1
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一款不错的聊天程序,可以与window的NetMeeting兼容!欢迎大家使用!...
一款不错的聊天程序,可以与window的NetMeeting兼容!欢迎大家使用!-one good chat program, with the NetMeeting window compatible! Everyone is welcome to use!
- 2023-04-17 21:35:03下载
- 积分:1
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利用Visual Basic编写的多功能计时器,能做秒表,也能做时钟。...
利用Visual Basic编写的多功能计时器,能做秒表,也能做时钟。-The use of Visual Basic preparation of multi-functional timer, stopwatch can also do clock.
- 2022-03-19 09:22:24下载
- 积分:1