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示例問題如下：
表結構:
Id ParentId
1 0
2 1
3 2
......

針對該表結構解釋如下:
1的父節點為0,
2的父節點為1,
3的父節點為2
......

以此類推,要求給定一個父節點的值,比如1,

用SQL語句查詢的到該父結點下的所有子節點

下面的Sql是在Sql Server下調試通過的,如果是Oracle,則有Connect By可以實現.

建立測試表:

Drop Table DbTree

Create Table DbTree

(

[Id] Int,

[Name] NVarChar(20),

[ParentId] Int

)

插入測試數據:

Insert Into DbTree ([Id],[ParentId]) Values (1,0)

Insert Into DbTree ([Id],[ParentId]) Values (2,1)

Insert Into DbTree ([Id],[ParentId]) Values (3,1)

Insert Into DbTree ([Id],[ParentId]) Values (4,3)

Insert Into DbTree ([Id],[ParentId]) Values (5,4)

Insert Into DbTree ([Id],[ParentId]) Values (6,7)

Insert Into DbTree ([Id],[ParentId]) Values (8,5)

實現方法一:

代碼如下:

Declare @Id Int

Set @Id = 1 ---在次修改父節點

Select * Into #Temp From DbTree Where ParentId In (@Id)

Select * Into #AllRow From DbTree Where ParentId In (@Id) --1,2

While Exists(Select * From #Temp)

Begin

Select * Into #Temp2 From #Temp

Truncate Table #Temp

Insert Into #Temp Select * From DbTree Where ParentId In (Select Id From #Temp2)

Insert Into #AllRow Select * From #Temp

Drop Table #Temp2

End

Select * From #AllRow Order By Id

Drop Table #Temp

Drop Table #AllRow

實現方法二:

代碼如下:

Create Table #AllRow

(

Id Int,

ParentId Int

)

Declare @Id Int

Set @Id = 1 ---在次修改父節點

Delete #AllRow

--頂層自身

Insert Into #AllRow (Id,ParentId) Select @Id, @Id

While @@RowCount > 0

Begin

Insert Into #AllRow (Id,ParentId)

Select B.Id,A.Id

From #AllRow A,DbTree B

Where A.Id = B.ParentId And

Not Exists (Select Id From #AllRow Where Id = B.Id And ParentId = A.Id)

End

Delete From #AllRow Where Id = @Id

Select * From #AllRow Order By Id

Drop Table #AllRow

實現方法三:

代碼如下:

在Sql Server2005中其實提供了CTE[公共表表達式]來實現遞歸:

關于CTE的使用請查MSDN

Declare @Id Int

Set @Id = 3; ---在次修改父節點

With RootNodeCTE(Id,ParentId)

As

(

Select Id,ParentId From DbTree Where ParentId In (@Id)

Union All

Select DbTree.Id,DbTree.ParentId From RootNodeCTE

Inner Join DbTree

On RootNodeCTE.Id = DbTree.ParentId

)

Select * From RootNodeCTE

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三種實現方法實現數據表中遍歷尋找子節點