How do I show nodes of a term and nodes of all it's subterms?

Did you check multiple select in the 'vocabulary' page.

check this option, then go back to each of your post and select 'secondary term1' hold down the 'control key' and select 'tertiar term 1' and so on. Save your post and there it is.

Hope this helps,

t4him
--*--
post back with your solution

I think the child/parent relationship in taxonomy is confusing. They does not appear to be any benefit to having child terms. The only effect is the display in the category select boxes.

You can use the views modules to do want you want. You can set it to display any of the selected terms.
http://drupal.org/project/views

here is a similiar question: http://drupal.org/node/58138
with a similiar answer ;)

White Paper Designs

...but you have to modify the modules/taxonomy.module file.
You should insert a new function into it, like:

function taxonomy_get_children_($tid, $vid = 0, $key = 'tid') {
  if ($vid) {
    $result = db_query(db_rewrite_sql('SELECT t.* FROM {term_data} t INNER JOIN {term_hierarchy} h ON h.tid = t.tid WHERE t.vid = %d AND h.parent = %d ORDER BY weight, name', 't', 'tid'), $vid, $tid);
  }
  else {
    $result = db_query(db_rewrite_sql('SELECT t.* FROM {term_data} t INNER JOIN {term_hierarchy} h ON h.tid = t.tid WHERE parent = %d ORDER BY weight, name', 't', 'tid'), $tid);
  }
  $children = array();
  while ($term = db_fetch_object($result)) {
    $children[] = $term->$key;
  }
  return $children;
}

(it's a hacked taxonomy_get_children function :) )
And change the taxonomy_select_nodes function like this:

function taxonomy_select_nodes($tids = array(), $operator = 'or', $depth = 0, $pager = TRUE, $order = 'n.sticky DESC, n.created DESC') {
  if (count($tids) > 0) {
    $children_tids = array();
    foreach ($tids as $index => $tid){
      if (taxonomy_get_children_($tid)){
        $children_tids[] = taxonomy_get_children_($tid);
      }
    }
    
    // For each term ID, generate an array of descendant term IDs to the right depth.
    $descendant_tids = array();
    if ($depth === 'all') {
      $depth = NULL;
    }
    foreach ($tids as $index => $tid) {
      $term = taxonomy_get_term($tid);
      $tree = taxonomy_get_tree($term->vid, $tid, -1, $depth);
      $descendant_tids[] = array_merge(array($tid), array_map('_taxonomy_get_tid_from_term', $tree));
    }

    if ($operator == 'or') {
      $str_tids = implode(',', call_user_func_array('array_merge', $descendant_tids + $children_tids));
      $sql = 'SELECT DISTINCT(n.nid), n.sticky, n.title, n.created FROM {node} n INNER JOIN {term_node} tn ON n.nid = tn.nid WHERE tn.tid IN ('. $str_tids .') AND n.status = 1 ORDER BY '. $order;
      $sql_count = 'SELECT COUNT(DISTINCT(n.nid)) FROM {node} n INNER JOIN {term_node} tn ON n.nid = tn.nid WHERE tn.tid IN ('. $str_tids .') AND n.status = 1';
    }
    else {
      $joins = '';
      $wheres = '';
      foreach ($descendant_tids as $index => $tids) {
        $joins .= ' INNER JOIN {term_node} tn'. $index .' ON n.nid = tn'. $index .'.nid';
        $wheres .= ' AND tn'. $index .'.tid IN ('. implode(',', $tids) .')';
      }
      if ($children_tids){
        foreach ($children_tids as $index => $tids) {
          $joins .= ' INNER JOIN {term_node} tnc'. $index .' ON n.nid = tnc'. $index .'.nid';
          $wheres .= ' OR tnc'. $index .'.tid IN ('. implode(',', $tids) .')';
        }
      }
      $sql = 'SELECT DISTINCT(n.nid), n.sticky, n.title, n.created FROM {node} n '. $joins .' WHERE n.status = 1 '. $wheres .' ORDER BY '. $order;
      $sql_count = 'SELECT COUNT(DISTINCT(n.nid)) FROM {node} n '. $joins .' WHERE n.status = 1 ' . $wheres;
    }
    $sql = db_rewrite_sql($sql);
    $sql_count = db_rewrite_sql($sql_count);
    if ($pager) {
      $result = pager_query($sql, variable_get('default_nodes_main', 10), 0, $sql_count);
    }
    else {
      $result = db_query_range($sql, 0, variable_get('feed_default_items', 10));
    }
  }

  return $result;
}

I haven't tested this too much, but it seems to be working.

See http://drupal.org/node/41349#comment-76913 for a possible solution.