trying to use batch_update()

In reading about group query I found this. But this is still not working any ideas?
````
            $this->db->select('*')->from('employees')
                ->group_start()
                ->where('email', $_SESSION['userid'])
                ->where('campaign', $_SESSION['campaign'])
                    ->or_group_start()
                    ->where('employee_title',  $exclude_string)
                    ->where('job_code',  $exclude_string)
                    ->where('department',  $exclude_string)
                    ->where('role',  $exclude_string)
                    ->group_end()
                ->group_end();
            $this->db->update('employees',$data );
````

proof that an old dog can learn new tricks