my @line;
foreach (my $top = $top_sth->fetchrow_hashref)
  {
  $line[0]= $top->{guid};
  push @line,$top->{title};
  $exchange->stdxls_write($exchange->stdxls_row(), \@line);
  print STDERR "Level1 ".$top->{title}."\n";

  child_levels($top->{asset_id},@line);
  }
$workbook->close();

sub child_levels
{
  my ($asset_id,@line) = @_;

  my $child_sth = $dbh->prepare('
    SELECT asset_id
      ,title
      ,seq
      ,guid
      ,parent_id
    FROM asset
    WHERE parent_id = ?
    ORDER BY seq
  ') or die $dbh->errstr;

  $child_sth->execute($asset_id) or die $child_sth->errstr;
  foreach (my $child = $child_sth->fetchrow_hashref)
    {
    $line[0]= $child->{guid};
    push @line,$child->{title};
    $exchange->stdxls_write($exchange->stdxls_row(), \@line);
    child_levels($child->{asset_id},@line);
    }