一个多级菜单树，如何删除一个父类下的全部子类
一个多级菜单树，父级和子级的关系是 父级的ID = 子级的PID
同理子级的ID = 孙级的PID 类推下去。有多少级不确定。
如果删除一个父级，则其下的所有子级，子级下面的N级都一起删除。

页面选择父级传到后台的父级的ID 就问下这样的删除语句该怎么写？ 是不是要用循环语句？

本人新手，请说详细点

------解决方案--------------------
BOM按节点排序应用实例 
--------------------------------------

-- Author : htl258(Tony)

-- Date : 2010-04-23 02:37:28

-- Version:Microsoft SQL Server 2008 (RTM) - 10.0.1600.22 (Intel X86) 

-- Jul 9 2008 14:43:34 

-- Copyright (c) 1988-2008 Microsoft Corporation

-- Developer Edition on Windows NT 5.1 <X86> (Build 2600: Service Pack 3)

-- Subject: BOM按节点排序应用实例

--------------------------------------

 

--实例1:

--> 生成测试数据表:tb

 

IF NOT OBJECT_ID('[tb]') IS NULL

DROP TABLE [tb]

GO

CREATE TABLE [tb]([id] INT,[code] NVARCHAR(10),[pid] INT,[name] NVARCHAR(10))

INSERT [tb]

SELECT 1,'01',0,N'服装' UNION ALL

SELECT 2,'01',1,N'男装' UNION ALL

SELECT 3,'01',2,N'西装' UNION ALL

SELECT 4,'01',3,N'全毛' UNION ALL

SELECT 5,'02',3,N'化纤' UNION ALL

SELECT 6,'02',2,N'休闲装' UNION ALL

SELECT 7,'02',1,N'女装' UNION ALL

SELECT 8,'01',7,N'套装' UNION ALL

SELECT 9,'02',7,N'职业装' UNION ALL

SELECT 10,'03',7,N'休闲装' UNION ALL

SELECT 11,'04',7,N'西装' UNION ALL

SELECT 12,'01',11,N'全毛' UNION ALL

SELECT 13,'02',11,N'化纤' UNION ALL

SELECT 14,'05',7,N'休闲装'

GO

--SELECT * FROM [tb]

 

-->SQL查询如下:

 

;WITH T AS

(

SELECT CAST(CODE AS VARCHAR(20)) AS CODE,*,

CAST(ID AS VARBINARY(MAX)) AS px 

FROM tb AS A

WHERE NOT EXISTS(SELECT * FROM tb WHERE id=A.pid)

UNION ALL 

SELECT CAST(B.CODE+A.CODE AS VARCHAR(20)),A.*,

CAST(B.px+CAST(A.ID AS VARBINARY) AS VARBINARY(MAX))

FROM tb AS A

JOIN T AS B

ON A.pid=B.id

)

SELECT Code,Name FROM T 

ORDER BY px

/*

Code Name

-------------------- ----------

01 服装

0101 男装

010101 西装

01010101 全毛

01010102 化纤

010102 休闲装

0102 女装

010201 套装

010202 职业装

010203 休闲装

010204 西装

01020401 全毛

01020402 化纤

010205 休闲装

 

(14 行受影响)

*/

 

--实例2:

--> 生成测试数据表:tb

IF NOT OBJECT_ID('[tb]') IS NULL
DROP TABLE [tb]
GO
CREATE TABLE [tb]([id] INT,[parentid] INT,[categoryname] NVARCHAR(10))
INSERT [tb]
SELECT 1,0,'test1' UNION ALL
SELECT 2,0,'test2' UNION ALL
SELECT 3,1,'test1.1' UNION ALL
SELECT 4,2,'test2.1' UNION ALL
SELECT 5,3,'test1.1.1' UNION ALL
SELECT 6,1,'test1.2'
GO
--SELECT * FROM [tb]

-->SQL查询如下:
;WITH T AS
(
SELECT *,CAST(ID AS VARBINARY(MAX)) AS px 
FROM tb AS A
WHERE NOT EXISTS(SELECT * FROM tb WHERE id=A.[parentid])
UNION ALL 
SELECT A.*,CAST(B.px+CAST(A.ID AS VARBINARY) AS VARBINARY(MAX))
FROM tb AS A
JOIN T AS B
ON A.[parentid]=B.id
)
SELECT [id],[parentid],[categoryname] FROM T 
ORDER BY px
/*
id paren