建树结构的原则就是先要有跟节点，才能建旗下的子节点，围绕这一矛盾展开，会有以下两种方法。

1.递归建树(数据表中有一个记录的parentid值为0，代表根节点)

procedure TForm1.createtree(Sender: TObject);
var
   sqlstr:string;
   i:Integer;
   rootnode,parentnode:TTreeNode;
   isfind:Boolean;
begin
   adoquery1.Close;
   ADOQuery1.SQL.Clear;
   sqlstr:=''select * from tdepart'';
   ADOQuery1.SQL.Add(sqlstr);
   ADOQuery1.Open;
   ADOQuery1.First;
   while not ADOQuery1.Eof do
     begin
       i:=0;
       isfind:=false;
       for i:=0 to tv1.Items.Count-1 do
         if ADOQuery1.fieldbyname(''departid'').Asinteger = integer(tv1.Items.item[i].Data) then
           begin
             isfind:=True;
             Break;
           end;
       if not isfind then
         createtreenode(ADOQuery1.fieldbyname(''departid'').Asinteger,
                        ADOQuery1.fieldbyname(''departname'').AsString,
                        ADOQuery1.fieldbyname(''parentid'').Asinteger);
       adoquery1.Next;             
     end;
end;

procedure TForm1.createtreenode(id:Integer;depart:string;parentid:integer);
var
   i,j,id1,parentid1:Integer;
   rootnode,parentnode:TTreeNode;
   isfind,isfind1:Boolean;
   sqlstr,depart1:string;
begin
       if parentid = 0 then
         rootnode:=tv1.Items.addchildobject(nil,trim(depart),pointer(id))
       else
         begin
           i:=0;
           parentnode:=nil;
           isfind:=false;
           for i:=0 to tv1.Items.Count-1 do
             if parentid = integer(tv1.Items.item[i].Data) then
               begin
              &nb