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yii源码三 -- db

2024-07-12 17:49:55   222人阅读

CDbConnection:
path:/framework/db/CDbConnection.php
overview:CDbConnection represents a connection to a database.

工作原理：CDbConnection works together with CDbCommand, CDbDataReader and CDbTransaction to provide data access to various DBMS。且基于PDO扩展。

　　首先用$connection = new CDbConnection($dsn,$username,$password)创建一个连接实例，然后调用$connection->active=true启动连接。

用法：
1.创建DB实例并建立连接：

$connection=new CDbConnection($dsn,$username,$password);$connection->active=true; //建立连接

2.执行sql语句:

$command=$connection->createCommand($sqlStatement);$command->execute();   //执行非查询语句(insert,delete,update)$reader=$command->query();//执行查询语句(select)

备注：预处理和绑定参数用法：

$command=$connection->createCommand($sqlStatement);$command->bindParam($name1,$value1);$command->bindParam($name2,$value2);$command->execute();

3.获取结果：

foreach($reader as $row){      ......  }

4.事务：

$transaction=$connection->beginTransaction();try{    $connection->createCommand($sql1)->execute();    $connection->createCommand($sql2)->execute();    //.... other SQL executions    $transaction->commit();}catch(Exception $e){    $transaction->rollback(); }

5.由于CDbConnection实现了IApplicationComponent接口，所以它可以当作一个application component并且在application配置文件(main.php)里配置数据库连接信息：

array(     ‘components‘=>array(         ‘db‘=>array(              ‘class‘=>‘CDbConnection‘,              ‘connectionString‘=>‘sqlite:path/to/dbfile‘,         ),     ),)


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