제가 사용하는 방법에서 질문한 내용으로 변경해 적어봅니다.
도움이 되면 좋겠네요...

procedure TForm.sbTreeClick(Sender: TObject);
var SqlText, s, sName: String;  i, j: integer;
    A, B: array[0..2] of string;
    xTreeNode : array[0..2] of TTreeNode;

  procedure TrimTreeView(TreeView: TTreeView);
  var i, j: integer;
  begin
    with TreeView do
    for i := 3 downto 0 do
    begin
      for j := Items.Count - 1 downto 0 do
      with Items[j] do
      if (Level = i) and (Text = '')
        and (Count = 0) then   Delete;
    end;
  end;

begin
  with Query1 do
  begin
    close;
    Sql.Text := 'SELECT DISTINCT Level,  MenuName' + cr
              + ' FROM TABLENAME ORDER BY Level';
    
    open;    
    TreeView.Items.Clear;

    first;
    for i := 0 to 2 do
    begin
      A[i] := '--dxt1';
      xTreeNode[i] := nil;
    end;

    while not Eof do
    begin
      s := fieldbyname('Level').asstring;
      sName := fieldbyname('MenuName').asstring
      B[0] := Copy(s, 1, 1);
      B[1] := Copy(s, 2, 1);
      B[2] := Copy(s, 3, 1);

      for i := 0 to 2 do
        if (A[i] <> B[i]) then
        begin
          A[i] := B[i];
          for j := i + 1 to 2 do A[j] := '--dxt1';
          if i = 0 then
            xTreeNode[i] := TreeView.Items.Add(nil, sName)
          else xTreeNode[i] := TreeView.Items.AddChild(xTreeNode[i-1], sName);
        end;
      next;
    end;

    close;
    TrimTreeView(TreeView);
    TreeView.Selected := TreeView.TopItem;
  end;
end;

전에 프로그램 하나 만들면서 짯던 부분이 있는데,
같은 기능을 할거같네요....
참조하세여....

<!--CodeS-->
var
    DepthString : TStringList;
    nameString  : TStringList;


procedure TpartForm.FormCreate(Sender: TObject);
var
    SqlString : String;
begin
    DepthString := TStringList.Create;
    nameString  := TStringList.Create;
    SqlString := 'select * from part ';
//    SqlString := SqlString + ' order by depth';
    ResetSQL(data.tempSQL, SqlString );
    partTree.Items.Add(partTree.selected, data.tempSQL.fieldbyname('name').asString);
    DepthString.Add(data.tempSQL.fieldbyname('depth').asString);
    data.TempSQL.Next;
    while (not data.tempSQL.Eof) do begin
        AddSubTree(data.tempSQL.fieldbyname('depth').asString,
                    data.tempSQL.fieldbyname('name').asString);
        data.TempSQL.Next;
    end;
end;

procedure TpartForm.AddSubTree(depth, name:String);
var
    depth1 : String;
    i, c ,temp     : byte;
    node : TTreenode;
begin
    c := partTree.Items.Count ;
    depth1 := copy(depth, 1, length(depth)-1);
    temp  := 0;
    for i := 0 to c - 1 do begin
        if(DepthString.Strings[i] = depth1) then begin
            node := partTree.Items.AddChild(partTree.items[i],
                data.tempSQL.fieldbyname('name').asString);
            DepthString.insert(node.Absoluteindex, depth);
            temp := 1;
            break;
        end
    end;
    if (temp = 0) then begin
        partTree.Items.Add(partTree.items[0], data.tempSQL.fieldbyname('name').asString);
        DepthString.Add(depth);
    end;
end;

<!--CodeE-->