1. Configuration files:
2. First add some definitions to index.php
3. Configuration file main.php

Configuration files: ¶

/index.php
/protected/config/main.php

First add some definitions to index.php ¶

//debug
defined('YII_DEBUG') or define('YII_DEBUG',true );
//show profiler
defined('YII_DEBUG_SHOW_PROFILER') or define('YII_DEBUG_SHOW_PROFILER',true);
//enable profiling
defined('YII_DEBUG_PROFILING') or define('YII_DEBUG_PROFILING',true);
//trace level
defined('YII_TRACE_LEVEL') or define('YII_TRACE_LEVEL',0);
//execution time
defined('YII_DEBUG_DISPLAY_TIME') or define('YII_DEBUG_DISPLAY_TIME',false);


require_once($yii);
Yii::createWebApplication($config)->run();

if(YII_DEBUG_DISPLAY_TIME)
echo Yii::getLogger()->getExecutionTime();

Definition YII_DEBUG_SHOW_PROFILER enables and disables profiler log with default db query log.
Definition YII_DEBUG_PROFILING enable profiling (YII_DEBUG_SHOW_PROFILER must be true to enable profiling).
Definition YII_TRACE_LEVEL yii trace level from 0 to 4.
Definition YII_DEBUG_DISPLAY_TIME display execution time at the end of application.

Configuration file main.php ¶

return array(
...
	'preload'=>array('log'),
...
	'components'=>array(
		'db'=>array(
			'connectionString' => 'mysql:host=localhost;dbname=dbname',
			'emulatePrepare' => true,
                        'enableProfiling' =>YII_DEBUG_PROFILING,
			'username' => 'username',
			'password' => 'password',
			'charset' => 'utf8',
		),
....        
                        'log'=>array(
                                'class'=>'CLogRouter',
                                'routes'=>array(
                                        array(
                                            'class' => 'CWebLogRoute',
                                            'enabled' =>YII_DEBUG_SHOW_PROFILER,
                                            'categories' => 'system.db.*',
                                            
                                        ),                                   
			),
		),
	),

);

Thats it :)