private function checkColumns($ok, $table, $cols)
    {
        $fords = false;
        foreach ($cols as $ck => $cv) {
          if ($cv instanceof Expression || $cv instanceof Select || is_string($cv)) {
            if ($ok === $ck) {
                $fords = $ok;
                break;
            } elseif (
              ($cv instanceof Expression && $ok === $cv->getExpression()) ||
              (str_replace('.','$',$ok) === $ck) ||
              (is_string($cv) && ($ok == $table . '.' . $cv) ) ) {
                $fords = $ck;
                break;
            }
          }
        }

        return $fords;
    }