Join in controller method

Hi how can i do a join query on controller's method :

Code:

$this->select('tratte_acquistate.*');
        $this->select('tratte_acquistate_extra.*');
        $this->select('tratte_acquistate_passeggeri.*');
        $this->from('tratte_acquistate');
        $this->join('tratte_acquistate_extra', 'tratte_acquistate.id = tratte_acquistate_extra.id_tratte_acquistate');
        $this->join('tratte_acquistate_passeggeri', 'tratte_acquistate_passeggeri.id = tratte_acquistate_passeggeri.id_tratte_acquistate');

        $this->orderBy('Table_3.id');
        $result = $this->findAll();

        echo $this->db->getLastQuery();

        return $result;

Call to undefined method App\Controllers\Admin_tratte_acquistate:: select()