请教一个关于treeview的问题，谢谢！！

我用下边代码做了一个treeview与数据库相连的小程序，但是在点击treeview的节点时老是出现‘缺少用于更新或刷新的基本表信息’的错误
不知道是怎么回事啊？下边是建立的三个数据表：
表 名      列 名       列 描 述  
SCHOOL    SCH_NO       学 校 编 号 
          SCH_NAME     学 校 名 称 
CLASS     CLS_NO       班 级 编 号  
          CLS_SCHNO    学 校 编 号  
          CLS_TEACHER  班 主 任 姓 名 
STUDENT   STU_NO       学 生 学 号 
          STU_NAME     学 生 姓 名  
          STU_BIRTHDAY 学 生 出 生 年 月 
          STU_ADDR     学 生 家 庭 地 址 
          CLS_NO       班级编号
一下是代码部分：先定义了一个全局变量：TempClassNo:string;   STUTable 的Filtered 属 性 为True
procedure TForm1.FormCreate(Sender: TObject);
　 　var
　 　  Node1,Node2,Node3:TTreeNode;
　 　  NodeText1,NodeText2:String;
　 　  TempValue:integer;
　 　begin
　 　 　with TreeView1.Items do
　 　 　begin
　 　 　 　clear;
　 　 　 　Node1:=Add(nil,' 学 校');// 添 加 根 节 点
                     // 指 定 显 示 在 节 点 文 字 的 图 标
　 　 　 　Node1.ImageIndex:=0;　     　// 打 开 三 个 数 据 表
　      　SCHTable.Active:=True;
          　 　CLASSTable.Active:=True;
          　 　STUTable.Active:=True;　 　 　 with SCHTable do
　 　 　 begin
　 　 　 　 　First;
　 　 　 　 　while not eof do
　 　 　 　 　begin
                                  // 获 得 学 校 的 名 称
　 　 　 　 　 　NodeText1:=Fields[1].AsString;
                                 // 获 得 学 校 的 编 号
　 　 　 　 　 　TempValue:=Fields[0].AsInteger;
                                // 插 入 一 个 学 校 节 点
　 　 　 　 　   Node2:=AddChild(Node1,NodeText1); 
                              // 指 定 学 校 节 点 前 的 图 标
　 　 　 　 　 　Node2.ImageIndex:=1;　 　 　 　 　 　with CLASSTable do
　 　 　 　 　 　begin
　 　 　 　 　 　 　First;
　 　 　 　 　 　 　while not eof do
　 　 　 　 　 　 　begin
                                             // 查 找 与 当 前 学 校 编 号 匹 配 的 班 级 记 录
     　 　 　 　 　 　 　if TempValue=Fields[1].AsInteger then 
　 　 　 　 　 　 　  begin
                                                 // 获 得 班 级 编 号
   　 　 　 　 　 　 　 　NodeText2:=Fields[0].AsString; 
                                               // 插 入 一 个 班 级 节 点
       　 　 　 　 　 　 　Node3:=AddChild(Node2,NodeText2); 
                                             // 指 定 班 级 节 点 前 的 图 标
　 　 　 　 　 　 　 　Node3.ImageIndex:=2;
　 　 　 　 　 　 　end;
　 　 　 　 　 　 　Next;
　 　 　 　 　 　end;
　 　 　 　 　end;
　 　 　 　 　Next;
　 　 　 　end;
　 　 　end;
　 　  end;　 　 　Treeview1.FullExpand;// 展 开 全 部 节 点
　 　 　// 关 闭 学 校、 班 级 表
　 　 　SCHTable.Close;
　 　 　CLASSTable.Close;
　 　end;
procedure TForm1.TreeView1MouseDown (Sender: TObject; Button: TMouseButton;Shift: TShiftState; X, Y: Integer);
　begin
　 　if TreeView1.Selected = nil then 
                Exit;
case  TreeView1.Selected.Level of
　 　 　0:  TreeView1.Selected.SelectedIndex:=3;
　 　 　1:  TreeView1.Selected.SelectedIndex:=4;
　 　 　2:  TreeView1.Selected.SelectedIndex:=5;
　 　end;
 // 该 值 将 传 递 给 表STUTable 的OnFiltereRecord 事 件 以 筛 选 被 选 中 班 级 的 学 生
      TempClassNo:=TreeView1.Selected.Text; 
 // 更 新 数 据 表， 激 发 表 STUTable 的OnFiltered 事 件。 
      STUTable.Refresh;  //在运行时可能是此处出错？
　end;
procedure TForm1.STUTableFilterRecord(DataSet:TDataSet;var Accept: Boolean);
begin
　Accept:=(STUTable.Fields[3].AsString=TempClassNo);
end;
请高手给我个详细的解答啊，非常感谢，高分相送！！