my $sth = $dbh->prepare(<<_EOSQL);
   select obj_id, type
   from   table
   where  parent_id = ?
_EOSQL

sub GetChildren
{
    my ($objid) = @_;
    for my $row (@{$dbh->selectall_arrayref, undef, $objid)})
    {
        if ($row->[1] eq 'Container')
        {
            GetChildren($row->[0]);
        }
        else
        {
            # whatever
        }
    }
}