delphi treeview根节点中添加节点的问题（急）

procedure loadUser(Sender: TObject; qry1, qry2: TADOQuery; tree: TspSkinTreeView; var treeNode1, treeNode2, treeNode3: TTreeNode);
//tree: TspSkinTreeView为皮肤控件类型

procedure TfrmUserMgr.loadUser(Sender: TObject; qry1, qry2: TADOQuery; tree: TspSkinTreeView; var treeNode1, treeNode2, treeNode3: TTreeNode);
begin
with qry1 do
begin
Close;
SQL.Clear;
SQL.Add('select * from user');
Open;
end;

Case qry1.fieldbyname('user_rights').AsInteger of
0:
begin
treeNode1 := tree.Items.Add(nil,'管理员');
with qry2 do
begin
Close;
SQL.Clear;
SQL.Add('select * from user where user_rights=0');
Open;
end;
while not qry2.Eof do
begin
tree.Items.Add(treeNode1,qry2.fieldbyname('user_name').AsString);
qry2.Next;
end;
end;

1:
begin
treeNode2:=tree.Items.Add(nil,'操作员');
with qry2 do
begin
Close;
SQL.Clear;
SQL.Add('select * from user where user_rights=1');
Open;
end;
while not qry2.Eof do
begin
tree.Items.Add(treeNode2,qry2.fieldbyname('user_name').AsString);
qry2.Next;
end;
end;

2:
begin
treeNode3:=tree.Items.Add(nil,'普通用户');
with qry2 do
begin
Close;
SQL.Clear;
SQL.Add('select * from user where user_rights=2');
Open;
end;
while not qry2.Eof do
begin
tree.Items.Add(treeNode3,qry2.fieldbyname('user_name').AsString);
qry2.Next;
end;
end;
qry1.next;
end;
end;
要实现
0---|管理员----|用户a
| |用户b
| |用户c
1---操作员----|用户d
| |用户e
| |用户f
2---|普通用户--|用户g
应该如何修改代码？现在能显示所有内容，但是比如操作员有N个用户，那么就会出现N个操作员的根节点，哪位大虾帮忙？

begin
treeNode2:=tree.Items.Add(nil,'操作员');
with qry2 do
begin
Close;
SQL.Clear;
SQL.Add('select * from user where user_rights=1');
Open;
end;
while not qry2.Eof do
begin
// 注意这里，只要把Add改成AddChild就可以了 tree.Items.AddChild(treeNode2,qry2.fieldbyname('user_name').AsString);
qry2.Next;
end;
end;


其它类同，
TTreeView.Items.Add是添加根结点
TTreeView.Items.AddChild是在第一个参数指示的节点下添加一个节点