我想创建一个拥有3级目录的树形数据储存结构,请问如何在表中嵌套一个表，又如何查询。

Question

有必要用嵌套表吗，树的级数问题应该用递归的方式可以解决啊 ！
id  nodename   parentid

Answer 1

干吗用嵌套表呀，我这里有一个我做的五级树，希望对你有所帮助这是我的一个工程中的treeview，虽然最后并没有选这个方案而是用了更灵活的树，但应对你有所帮助楼主将各列的值换位一个列中不同位置的数值数据即可！
  leiflag = False
        sheng = ""
        shi = ""
        lei = ""
        te = ""
        Try            Dim mynodes As TreeNodeCollection
            Dim i As Integer = 0, j As Integer = 0, k As Integer = 0, l As Integer = 0, m As Integer = 0            strsql = "SELECT 单位所在省, 单位所在市, 单位类别,特点一,特点二 FROM pc_company ORDER BY 单位所在省, 单位所在市,单位类别,特点一 "
            sqlcom = New SqlCommand(strsql, conn)
            conn.Open()
            dr = sqlcom.ExecuteReader
            While dr.Read                If dr.GetString(0) <> sheng Then
                    j = 0
                    k = 0
                    l = 0
                    m = 0                    sheng = dr.GetString(0)
                    shi = dr.GetString(1)
                    lei = dr.GetString(2)
                    te = dr.GetString(3)                    With TreeView1
                        .Nodes.Add(dr.GetString(0))
                        .SelectedNode = .Nodes(i)
                        i = i + 1                        .SelectedNode.Nodes.Add(dr.GetString(1))
                        .SelectedNode = .SelectedNode.Nodes(j)
                        j = j + 1                        .SelectedNode.Nodes.Add(dr.GetString(2))
                        .SelectedNode = .SelectedNode.Nodes(k)
                        k = k + 1                        .SelectedNode.Nodes.Add(dr.GetString(3))
                        .SelectedNode = .SelectedNode.Nodes(l)
                        l = l + 1                        .SelectedNode.Nodes.Add(dr.GetString(4))
                        .SelectedNode = .SelectedNode.Nodes(m)
                        m = m + 1
                    End With                Else
                    If dr.GetString(1) <> shi Then
                        shi = dr.GetString(1)
                        lei = dr.GetString(2)
                        te = dr.GetString(3)
                        k = 0
                        l = 0
                        m = 0
                        With TreeView1
                            .SelectedNode.Parent.Parent.Parent.Parent.Nodes.Add(dr.GetString(1))
                            .SelectedNode = .SelectedNode.Parent.Parent.Parent.Parent.Nodes(j)
                            j = j + 1                            .SelectedNode.Nodes.Add(dr.GetString(2))
                            .SelectedNode = .SelectedNode.Nodes(k)
                            k = k + 1                            .SelectedNode.Nodes.Add(dr.GetString(3))
                            .SelectedNode = .SelectedNode.Nodes(l)
                            l = l + 1                            .SelectedNode.Nodes.Add(dr.GetString(4))
                            .SelectedNode = .SelectedNode.Nodes(m)
                            m = m + 1
                        End With
                    Else
                        If dr.GetString(2) <> lei Then
                            lei = dr.GetString(2)
                            te = dr.GetString(3)
                            l = 0
                            m = 0                            With TreeView1
                                .SelectedNode.Parent.Parent.Parent.Nodes.Add(dr.GetString(2))
                                .SelectedNode = .SelectedNode.Parent.Parent.Parent.Nodes(k)
                                k = k + 1                                .SelectedNode.Nodes.Add(dr.GetString(3))
                                .SelectedNode = .SelectedNode.Nodes(l)
                                l = l + 1                                .SelectedNode.Nodes.Add(dr.GetString(4))
                                .SelectedNode = .SelectedNode.Nodes(m)
                                m = m + 1
                            End With
                        Else
                            If dr.GetString(3) <> te Then
                                te = dr.GetString(3)
                                m = 0
                                With TreeView1                                    .SelectedNode.Parent.Parent.Nodes.Add(dr.GetString(3))
                                    .SelectedNode = .SelectedNode.Parent.Parent.Nodes(l)
                                    l = l + 1                                    .SelectedNode.Nodes.Add(dr.GetString(4))
                                    .SelectedNode = .SelectedNode.Nodes(m)
                                    m = m + 1
                                End With
                            Else
                                With TreeView1
                                    .SelectedNode.Parent.Nodes.Add(dr.GetString(4))
                                    .SelectedNode = .SelectedNode.Parent.Nodes(m)
                                    m = m + 1
                                End With
                            End If                        End If
                    End If
                End If
            End While
            conn.Close()
            TreeView1.CollapseAll()
            '''CallRecursive(TreeView1)
        Catch err As Exception
            MsgBox(err.ToString)
        End Try

Answer 2

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'Put user code to initialize the page here
if not ispostback then
      sqlpara1 = New SqlParameter("@parentdocid", Session("parentdocid"))
        coll = New Collection()
        coll.Add(sqlpara1)
        ds = New DataSet()
        ds = OA.RunStoreProcReturn("Email_BoundUserDOC", coll)
        Session("ds") = ds
         BoundTreeview(TreeView1.Nodes, 0)
end if
    End Sub Private Sub BoundTreeview(ByRef TreeNodes As TreeNodeCollection, ByVal ParentID As Integer)
        'DocName,DocumentID,ParentDocID
        Dim ds As New DataSet()
        ds = Session("ds")
        Dim treeDV As New DataView()
        Dim treeDVrow As DataRowView
        Dim treeId As Integer
        Dim treeTemp As TreeNode
        Dim treeName As String
        treeDV.Table = ds.Tables(0)
        treeDV.RowFilter = "parentdocid='" & ParentID & "'"
        For Each treeDVrow In treeDV
            treeTemp = New TreeNode()
            treeName = treeDVrow("DocName")
            treeId = treeDVrow("DocumentID")
            treeTemp.ID = treeId
            treeTemp.Text = treeName
            TreeNodes.Add(treeTemp)
            BoundTreeview(TreeNodes(TreeNodes.Count - 1).Nodes, treeId)
        Next
    End Sub

Answer 3

可以看看这个，我写的代码：
http://expert.csdn.net/Expert/topic/1308/1308130.xml?temp=.3259546