$rows = $db->select('*')->from('tabulka')->fetchAssoc('id');
foreach ($rows as $id => $row) {
    if (!$row['parent']) {
        continue;
    }

    $rows[$row['parent']]['children'][] = $row;
    unset($rows[$id]);
}

// šanblona

<ul n:block="#tree">
    <li n:foreach="$rows as $row">{$row['nazev']}
        {ifset $row['children']}
            {include #tree, $rows => $row['children']}
        {/ifset}
    </li>
</ul>