user authantication problem

Yii 1.1 General Discussion
1

how to add some validation which check that the user name you want to enter is already exist in database …

thanks

2 

            array('UserName', 'unique',

                'on'=>'insert,update,signup',

                'message'=>t('Not available')

            ),
3

check the CExistValidator - http://www.yiiframework.com/doc/api/CExistValidator

4

thank u brother. you have solved my problem.