我想用Tree的形式实现如下目的怎么做？(100分)

我想达到如下的目的，最后的效果是这样：
100--- 一片区
1001-- 金门
1002-- 南环
1003-- 石湖
200--- 二片区
2001---金鸡湖
2002---永安
2003---桐泾
300-- 三片区
3001---沁园
3002---时代
3003---苏油
400--- 四片区
4001--- 苏安
4002---杏秀桥
4003---西垮塘

以上可以自由增加删除查询片区以及可以自由增加删除查询其下面的单位，
怎样设计其数据库的结构，和怎么用Tree的递归来实现，提供原代码参考！
谢谢！

你把数据库中的表结构贴出来

我做了一个DBTreeView控件，只要有以下字段即可
fid //自动增加类型
fPid //父ID
fdisplayname //字段显示名称
源代码如下：
{
Author: Deityfox
Email: Deityfox@163.com
Homepage: http://www.pfans.net/
QQ: 58193693
Date: 2002/11/23
CopyRight(C) 2001-2002 FoxStuio
}
unit DBTreeViewEx;

interface

uses
Windows, Messages, SysUtils, Classes, Controls,forms, ComCtrls,DB;
type
TDBTreeViewEx = class(TTreeView)
private
{ Private declarations }
FParentField:TIntegerField;
FChildField:TIntegerField;
FDisplayField:TStringField;
FDataLink:TDataLink;
FActive:Boolean;
//SubItems:TStrings;
FOnChanged: TNotifyEvent;
Procedure SetParentField(const aField:TIntegerField);
Procedure SetChildField(const aField:TIntegerField);
Procedure SetDisplayField(const aField:TStringField);
Function GetDataSource:TDataSource;
Procedure SetDataSource(ads:TDataSource);
Procedure FillContents(aParent:String;Node:TTreeNode);
Procedure SetActive(const aActive:Boolean);
protected
procedure Collapse(Node: TTreeNode);override;
procedure Expand(Node: TTreeNode);override;
{ Protected declarations }
public
Constructor Create(Owner:TComponent);Override;
Destructor Destroy;Override;
{ Public declarations }
published
Property ParentField:TIntegerField Read FParentField Write SetParentField;
Property ChildField:TIntegerField Read FChildField Write SetChildField;
Property DisplayField:TStringField Read FDisplayField Write SetDisplayField;
Property DataSource:TDataSource Read GetDataSource Write SetDataSource;
Property Active:Boolean Read FActive Write SetActive;
Property OnChanged:TNotifyEvent read FOnChanged write FOnChanged;
{ Published declarations }
end;

procedure Register;

implementation

Constructor TDBTreeViewEx.Create(Owner:TComponent);
Var I:Integer;
begin
Inherited Create(Owner);
FDataLink:=TDataLink.Create;
FDataLink.DataSource:=nil;
FParentField:=nil;
FChildField:=nil;
FDisplayField:=nil;
Active:=False;
if owner is TForm then
begin
for I:=0 to TForm(owner).ComponentCount-1 do
begin
if TForm(owner).Components is TImageList then
begin
Images:=TForm(Owner).Components as TImageList;
break;
end;
end;
end;
end;

Function TDBTreeViewEx.GetDataSource:TDataSource;
begin
Result:=FDataLink.DataSource;
end;

Procedure TDBTreeViewEx.SetDataSource(ads:TDataSource);
begin
if ads<>FDataLink.DataSource then
FDataLink.DataSource:=ads;
end;

Procedure TDBTreeViewEx.SetParentField(const aField:TIntegerField);
begin
if aField<>FParentField then FParentField:=aField;
if (FParentField<>nil) and (FChildField<>nil) and (FDisplayField<>nil)
and (Assigned(FDataLink.DataSource)) and Assigned(FDataLink.DataSource.DataSet) then
begin
Items.Clear;
FillContents('0',Nil);
FActive:=True;
end;
end;

Procedure TDBTreeViewEx.SetChildField(const aField:TIntegerField);
begin
if aField<>FChildField then FChildField:=aField;
if (FParentField<>nil) and (FChildField<>nil) and (FDisplayField<>nil)
and (Assigned(FDataLink.DataSource)) and Assigned(FDataLink.DataSource.DataSet) then
begin
Items.Clear;
FillContents('0',Nil);
FActive:=True;
end;
end;

Procedure TDBTreeViewEx.SetDisplayField(const aField:TStringField);
begin
if aField<>FDisplayField then FDisplayField:=aField;
if (FParentField<>nil) and (FChildField<>nil) and (FDisplayField<>nil)
and (Assigned(FDataLink.DataSource)) and Assigned(FDataLink.DataSource.DataSet) then
begin
Items.Clear;
FillContents('0',Nil);
Active:=True;
end;
end;

Procedure TDBTreeViewEx.FillContents(aParent:String;Node:TTreeNode);
Var
aNode:TTreeNode;
ChildList:TStrings;
DisplayList:TStrings;
I:Integer;
begin
ChildList:=TStringList.Create;
DisplayList:=TStringList.Create;
With DataSource.DataSet do
begin
Filtered:=False;
Filter:=FParentField.FieldName+'='+aParent;
Filtered:=True;
First;
While Not Eof do
begin
ChildList.Add(FChildField.AsString);
DisplayList.Add(FDisplayField.AsString);
Next;
end;
For I:=0 to ChildList.Count-1 do
begin
aNode:=Items.AddChildObject(Node,DisplayList.Strings,pointer(strtoint(ChildList.Strings)));
aNode.ImageIndex:=1;
FillContents(ChildList.Strings,aNode);
end;
Filtered:=False;
ChildList.Free;
DisplayList.Free;
end;
Selected:=Items[0];
end;

Procedure TDBTreeViewEx.SetActive(const aActive:Boolean);
begin
if FActive=aActive then Exit;
if Not aActive then
begin
Items.Clear;
FActive:=False;
end else
begin
if (FParentField<>nil) and (FChildField<>nil) and (FDisplayField<>nil)
and (Assigned(FDataLink.DataSource)) and Assigned(FDataLink.DataSource.DataSet) then
begin
Items.Clear;
FillContents('0',Nil);
FActive:=True;
end;
end;
if Assigned(OnChanged) then OnChanged(Self);
end;

procedure TDBTreeViewEX.Collapse(Node: TTreeNode);
begin
Node.ImageIndex:=1;
inherited;
end;

procedure TDBTreeViewEx.Expand(Node: TTreeNode);
begin
Node.ImageIndex:=2;
inherited;
end;



procedure Register;
begin
RegisterComponents('FoxStudio', [TDBTreeViewEx]);
end;


destructor TDBTreeViewEx.Destroy;
begin
FDataLink.Free;
inherited Destroy;
end;

end.

bom 结构
f_id f_parent_id f_name

参考：http://www.delphibbs.com/delphibbs/dispq.asp?lid=1457841