数据库的访问（三）
任何数据库的访问都是建立在链接的接触上。 根据我目前的理解，暂时用到的连接方式有三种：如图（思维导图） 第一种、使用 ADO 之间连接数据库 在连接的字符串中必须指定正确的数据提供者（ Provider ）、数据库、数据库服务器、访问数据库身份验证方式以及
任何数据库的访问都是建立在链接的接触上。
根据我目前的理解，暂时用到的连接方式有三种：如图（思维导图）
第一种、使用ADO之间连接数据库
在连接的字符串中必须指定正确的数据提供者（Provider）、数据库、数据库服务器、访问数据库身份验证方式以及用户名、口令等信息。
Connection连接对象，用于创建数据源的链接。在使用其他对象和访问数据源之前必须先建立数据源的链接，然后再连接对象上创建和使用其他对象。
快速获得字符串链接的方法：
1、打开一个“记事本”另存为扩张名为.udl的文件图1
2、双击刚建文件打开“数据连接属性对话框”在提供程序选择一个提供者图2
3、在连接中填写所需信息图3
4、测试成功之后点“确定”。再用记事本打开文件即可看到图4
第二种、ADO—ODBC---数据库
用户DSN：计算机本地数据源，把相应的配置信息保存在Windows的注册表中，只能被当前用户使用
文件DSN：计算机本地数据源，可被任何具有权限的用户使用
系统DSN：可以不是计算机本地数据源，将有关的配置信息保存在系统注册表中，可被安装了相同驱动程序的用户共享，即是允许所有登录服务器的用户使用。
odbc中提供三种dsn,它们的区别很简单：用户dsn只能用于本用户。系统dsn和文件dsn的区别只在于连接信息的存放位置不同：系统dsn存放在odbc储存区里，而文件dsn则放在一个文本文件中。（还要在网上查一下）
至于配置步骤这里不再详述。
eg：
链接sql server:
用系统dsn: connstr="DSN=dsnname; UID=xx;PWD=xxx;DATABASE=dbname"
用文件dsn: connstr="FILEDSN=xx; UID=xx; PWD=xxx;DATABASE=dbname"
第三种、使用数据绑定控件，可以不写代码
ADO Data控件使用ADO来快速建立数据绑定的控件和数据提供者之间的链接，他对用户隐藏了对ADO对象的编程。使用该控件可通过在属性窗口中设置相应的属性来建立数据源链接，然后通过数据绑定操作将获得的记录集绑定到特定的控件，显示在窗体。同时也可以通过控件的响应事件过程写入极少的代码完成数据库的操作（红皮书上的实例三）
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