Some ways to use multiple database connection in Yii framework.

1. Declare more database Connection in config file

To use multiple database connection you can try putting another db component into the configuration file at protected/config/main.php

array(
'components'=>array(
    'db'=>array(
  'connectionString' => 'mysql:host=localhost;dbname=yii_blog',
  'emulatePrepare' => true,
  'username' => 'YOUR_USERNAME',
  'password' => '*************',
  'charset' => 'utf8',
  'tablePrefix' => 'tbl_',
  ),
    'anotherDb' => array(
            'connectionString' => 'mysql:host=adserver2;dbname=anotherDB',
            'username'         => 'YOUR_USERNAME',
            'password'         => '***********',
            ...
            'class'            => 'CDbConnection'          // DO NOT FORGET THIS!
             ),
),
The parameters should generally follow the pattern of the first entry, but you must include the class parameter ('class' => 'CDbConnection' ) in the second so that Yii knows you're defining a DB Connection object. It will fail without this.

You can access them by calling like that

$firstDb = Yii::app()->db;
$firstDb->active = true;
// etc, then
$secondDb = Yii::app()->anotherDb;
$secondDb->active = true;

or GetDbConnection() override in model class like the following: 
    class YourModel extends CActiveRecord {
    ...
    private $anotherDb = null;
 
    protected function getDbConnection()
    {
        if (self::$anotherDb !== null)
            return self::$anotherDb;
        else
        {
            self::$anotherDb = Yii::app()->anotherDb;
            if (self::$anotherDb instanceof CDbConnection)
            {
                self::$anotherDb->setActive(true);
                return self::$anotherDb;
            }
            else
                throw new CDbException(Yii::t('yii','Active Record requires'.
                           'a "db" CDbConnection application component.'));
        }
    }
Note: This entry will be update more if We know another way to do