delphi order by排序问题：请各位帮检查一写法有何错误，谢谢
procedure TForm8.Button2Click(Sender: TObject);
begin
ADOQuery1.close;
ADOQuery1.SQL.Clear;
ADOQuery1.SQL.add('select * from insp order by');
ADOQuery1.SQL.add(ADOQuery1.FieldCount.Items[ComBoBox1.ItemIndex].FieldName);
if CheckBox1.Checked then
begin
ADOQuery1.SQL.Add('Desc');
end;
end;

请帮我看下红色的一行有什么错误，谢谢！

[解决办法]
ADOQuery1.SQL.add(ADOQuery1.Fields[ComBoBox1.ItemIndex].FieldName);