sql update codeigniter
===

I am using codeIgniter..
I want to update a table column `is_close` when `id=$ticket_id` of my `table= tbl_tickets.`
I am doing this :-

    $data=array(
                'is_close'=>1
                );
            $this->db->where('id',$title_id);
            $this->db->update('tbl_tickets',$data);

and I have also done this :-

    $sql = "UPDATE tbl_tickets SET is_close={1} WHERE id='$title_id'";
    $this->db->query($sql);

both are not working,i.e., my table is not updating the value to 1 and also no error is being shown in the broswer. :(