code: public function asSQL($force_braces = null)
    {
      $arr = array();
      if ($this->conditions) {
        foreach ($this->conditions as $cond) {
          $arr[] = $cond->asSQL(
            is_null($force_braces)
              ? $cond instanceof Conditions && !$this->join_by_and
              : $force_braces
          );
        }
      }
  
      return $this->processPieces($arr, $force_braces);
    }
docs: Условие в виде запроса SQL