TreeView, Delphi, MySQL

var
  CurrentDeptID, RecordDeptID, RecordDeptID_s, CurrentDeptID_s: Integer;
  RootNode, DeptNode, ThreeNode: TTreeNode;
begin
  ZQuery1.Connection := Main_menu.ZConnection1;
  CurrentDeptID := 0;
  CurrentDeptID_s := 0;
  TreeView1.Items.Clear;
  RootNode := TreeView1.Items.Add(nil, 'Microscheme');
  DeptNode := nil;
  ThreeNode := nil;
  ZQuery1.SQL.Text := 'SELECT sd.id_c, sd.id_s, d.type_c, sd.type_s, m.name FROM category d LEFT JOIN scategory sd ON (sd.id_c = d.id_c) LEFT JOIN ms m ON (sd.id_s = m.id_s) ';
  ZQuery1.Open;
  try
    ZQuery1.First;
    while not ZQuery1.Eof do
    begin
      RecordDeptID := ZQuery1.FieldByName('id_c').AsInteger;
      RecordDeptID_s := ZQuery1.FieldByName('id_s').AsInteger;
      if (DeptNode = nil) or (RecordDeptID <> CurrentDeptID) then
      begin
        DeptNode := TreeView1.Items.AddChild(RootNode,ZQuery1.FieldByName('type_c').AsString);
        CurrentDeptID := RecordDeptID;
        if (ThreeNode = nil) or (RecordDeptID_s <> CurrentDeptID_s) then
        begin
          ThreeNode := TreeView1.Items.AddChild(DeptNode, ZQuery1.FieldByName('type_s').AsString);
          CurrentDeptID_s := RecordDeptID_s;
        end;
      end;
        TreeView1.Items.AddChild(ThreeNode, ZQuery1.FieldByName('name').AsString);
      ZQuery1.Next;
 
    end;
  finally
    ZQuery1.Close;
    end;

Query1.SQL.Text := 'SELECT id_c, type_c as name FROM category ';
DataSource1.DataSet = Query1;
Query2.SQL.Text := 'SELECT id_s, type_s as name FROM scategory WHERE id_c = :id_c';
DataSource2.DataSet = Query2;
Query2.DataSource = DataSource1;
Query3.SQL.Text := 'SELECT name FROM ms WHERE id_s = :id_s ';
Query3.DataSource = DataSource2;