my @nodes = ();

my $sth = $dbh->prepare(q{
   SELECT node_id, title, body FROM node WHERE parent_id = ?
});

$sth->execute($parent_id);
while (my $row = $sth->fetchrow_hashref) {
    push @nodes, $row;
}
$sth->finish;

foreach my $node (@nodes) {

    $sth->execute($node->{node_id});
    $node->{children} = $sth->fetchall_arrayref({
                            node_id => 1, title => 1
                        });
    $sth->finish;
}

$t->param(NODES => \@nodes);