Rank Per Group Not Working In Yii Php

I am trying to execute rank per group query in yii framework to show results in a CGridview, but it is giving error, Here is my code in controller.

   $sql = "SELECT t.ID as ID,


        t.count as Count


        FROM (


        SELECT t.*,


                @rank:= CASE WHEN @group = t.ID THEN @rank +1 ELSE 1 END rank ,


                @group:= t.ID 


        FROM


            (   SELECT p1.emp_id as ID , p1.project_id as item,


                        (select count(s.project_id) 


                            from EmployeeStats s 


                            where s.project_id = p1.project_id 


                            and s.action = 'START' 


                            and s.time BETWEEN '$from'  AND '$to'


                        ) as count


            FROM ManagerEmployee p1


            where p1.manager_id in(select p.id from Manager p where p.type = 'X')


            group by p1.project_id


            ORDER BY p1.manager_id


            )as t


        ORDER BY t.ID ,t.count  DESC


    ) t WHERE t.rank <=3";








$rawData = Yii::app()->db->createCommand($data);





return $perGenre = new CSqlDataProvider($rawData,array(


        'keyField'=>'ID',


        'pagination'=>array(


                'pageSize'=>10,


        )


));

I have tested the above query($sql) in Mysql workbench it is working and giving desire results, but when i execute the above code in yii framework it is giving me following error

CDbCommand failed to execute the SQL statement: SQLSTATE[42000]:

Syntax error or access violation: 1064 You have an error in your SQL syntax;

check the manual that corresponds to your MySQL server version for the right syntax to use near

‘FROM (\n\t\t\t\tSELECT t.*,\n\t\t\t\t\t\t@rank:= CASE WHEN @group = t.genre THEN @rank +1 EL’ at line 5

i have also added following below lines at the top of $sql query string .

"SET @rank=0; SET @group=’’;

But it is giving

CDbCommand failed to execute the SQL statement: SQLSTATE[HY000]: General error

Please help me to figure out a, why rank per group is not working in framework?