TreeView控件在编制程序过程中用得比较多。正确的掌握和使用这个控件，可以很好的表示层次关系的数据。在数据库应用系统中，我们可以用TreeView来显示树形结构，如显示目录树、显示班级信息等等，有着很重要的作用
看看下面一个实际的问题：每个年度都有许多的班级，将这些数据层次表示
数据库:access
表:Test
字段:bh(班级编号,文本，主键),nj(年级,文本)
功能：以层次关系表现出数据
测试数据：
bh
nj
41020
2001
41021
2001
41025
2003
41026
2003
41027
2003
41028
2003
添加TreeView控件，2个按钮
2个按钮分别用了两种方法显示数据。但是第二种方法明显优于第一种。
可以仔细的看代码
'引用microsoft activex data object 2.x library
Dim nddata As Node
Dim cnn As ADODB.Connection
Dim rs1 As New ADODB.Recordset
Dim rs2 As New ADODB.Recordset
Private Sub Command1_Click()
On Error Resume Next
Set nddata = TreeView1.Nodes.Add(, , "db", "班级信息")
nddata.Expanded = True
Dim intcount As Integer
Dim inttable As Integer
Dim intfield As Integer
Dim intfn As Integer
rs1.Open "select nj from test group by nj", cnn, 1, 3
inttable = rs1.RecordCount
Do While inttable <> intcount
Set nddata = TreeView1.Nodes.Add("db", tvwChild, "F" & rs1.Fields("nj"), rs1.Fields("nj"))
rs2.Open "select bh,nj from test where nj='" & rs1.Fields("nj") & "'", cnn, 1, 3
intfield = rs2.RecordCount
If intfield <> 0 Then
intfn = 0
Do While intfield <> intfn
Set nddata = TreeView1.Nodes.Add("F" & rs1.Fields("nj"), tvwChild, "S" & rs2.Fields("bh"), rs2.Fields("bh"))
rs2.MoveNext
intfn = intfn + 1
Loop
End If
rs2.Close
rs1.MoveNext
intcount = intcount + 1
Loop
rs1.Close
End Sub
‘第二种方法
Private Sub Command2_Click()
On Error Resume Next
Set nddata = TreeView1.Nodes.Add(, , "db", "班级信息")
nddata.Expanded = True
rs1.Open "select * from test", cnn, 1, 3
Do While Not rs1.EOF
If ca <> rs1.Fields("nj") Then
Set nddata = TreeView1.Nodes.Add("db", tvwChild, "F" & rs1.Fields("nj"), rs1.Fields("nj"))
ca = rs1.Fields("bb")
End If
Set nddata = TreeView1.Nodes.Add("F" & rs1.Fields("nj"), tvwChild, "S" & rs1.Fields("bh"), rs1.Fields("bh"))
rs1.MoveNext
Loop
rs1.Close
End Sub
Private Sub Form_Load()
Set cnn = New ADODB.Connection
cnn.Open "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=F:\csdn_vb\database\treeview的节点添加\1\test.mdb"
End Sub
Private Sub Form_Unload(Cancel As Integer)
Set con = Nothing
End Sub