表usertree的结构和记录为
id(数值弄)  parentid(字符弄)   name(字符弄)
1                   0                   全校
2                   1                   99级
3                   1                   00级
4                   2                  9901班
5                   3                  990101专业
6                   2                  0001班
7                   3                  000101专业 
。。
rsusertree.Open "select  * FROM usertree", conn, 3, 3
    Do Until rsusertree.EOF
        If rsusertree!parentid = 0 Then
            TreeView1.Nodes.Add , , "Nvv" & rsusertree!ID, rsusertree!Name
        Else
            TreeView1.Nodes.Add "Nvv" & rsusertree!parentid, tvwChild, "Nvv" & rsusertree!ID, rsusertree!Name
        End If
        rsusertree.MoveNext
    Loop
    Dim i As Integer
    For i = 1 To Me.TreeView1.Nodes.Count
        Me.TreeView1.Nodes(i).Expanded = True
    Next i
     conn.Close
运行时生成不正确的分层的树结构,如何识别在对应的级点而生成正确的分层的树结构,当在某级点下增加级点时,应先加记录到数据库中,表usertree的结构要变吗?如何知id,parentid的数值呢?