--测试数据
CREATE TABLE tb(ID char(3),PID char(3),Name nvarchar(10))
INSERT tb SELECT '001',NULL ,'山东省'
UNION ALL SELECT '002','001','烟台市'
UNION ALL SELECT '004','002','招远市'
UNION ALL SELECT '003','001','青岛市'
UNION ALL SELECT '005',NULL ,'四会市'
UNION ALL SELECT '006','005','清远市'
UNION ALL SELECT '007','006','小分市'
GO

--查询指定节点及其所有子节点的函数
CREATE FUNCTION f_Cid(@ID char(3))
RETURNS @t_Level TABLE(ID char(3),Level int)
AS
BEGIN
    DECLARE @Level int
    SET @Level=1
    INSERT @t_Level SELECT @ID,@Level
    WHILE @@ROWCOUNT>0
    BEGIN
        SET @Level=@Level+1
        INSERT @t_Level SELECT a.ID,@Level
        FROM tb a,@t_Level b
        WHERE a.PID=b.ID
            AND b.Level=@Level-1
    END
    RETURN
END
GO

--调用函数查询002及其所有子节点
SELECT a.*
FROM tb a,f_Cid('002') b
WHERE a.ID=b.ID
/*--结果
ID   PID  Name       
------ ------- ---------- 
002  001  烟台市
004  002  招远市
--*/

------解决方案--------------------

SQL code
CREATE FUNCTION f_Pid(@ID char(3))
RETURNS @t_Level TABLE(ID char(3),Level int)
AS
BEGIN
    DECLARE @Level int
    SET @Level=1
    INSERT @t_Level SELECT @ID,@Level
    WHILE @@ROWCOUNT>0
    BEGIN
        SET @Level=@Level+1
        INSERT @t_Level SELECT a.PID,@Level
        FROM tb a,@t_Level b
        WHERE a.ID=b.ID
            AND b.Level=@Level-1
    END
    RETURN
END
GO


--上面的用户定义函数可以处理一个节点有多个父节点的情况，对于标准的树形数据而言，由于每个节点仅有一个父节点，所以也可以通过下面的用户定义函数实现查找标准树形数据的父节点。
CREATE FUNCTION f_Pid(@ID char(3))
RETURNS @t_Level TABLE(ID char(3))
AS
BEGIN
    INSERT @t_Level SELECT @ID
    SELECT @ID=PID FROM tb
    WHERE ID=@ID
        AND PID IS NOT NULL
    WHILE @@ROWCOUNT>0
    BEGIN
        INSERT @t_Level SELECT @ID
        SELECT @ID=PID FROM tb
        WHERE ID=@ID
            AND PID IS NOT NULL
    END
    RETURN
END

------解决方案--------------------

SQL code
create table tb(id int,parentid int,sname varchar(10))
insert into tb select 1 , -1     ,    '根节点' 
insert into tb select 2 ,  1     ,    '节点1' 
insert into tb select 3 ,  1     ,    '节点2' 
insert into tb select 4 ,  2     ,    '节点3' 
insert into tb select 5 ,  2     ,    '节点4' 
insert into tb select 6 ,  3     ,    '节点5' 
insert into tb select 7 ,  3     ,    '节点6' 
insert into tb select 7 ,  6     ,    '节点7' 
go

CREATE FUNCTION f_Cid(@ID int)
RETURNS @t_Level TABLE(ID int,Level int)
AS
BEGIN
    DECLARE @Level int
    SET @Level=1
    INSERT @t_Level SELECT @ID,@Level
    WHILE @@ROWCOUNT>0
    BEGIN
        SET @Level=@Level+1
        INSERT @t_Level SELECT a.ID,@Level
        FROM tb a,@t_Level b
        WHERE a.parentID=b.ID
            AND b.Level=@Level-1
    END
    RETURN
END
GO

select distinct a.* 
from f_cid(3) b ,tb a
where b.id=a.id
  and not exists(select * from tb where parentid=b.id)


go
drop table tb
drop function f_cid

/*
id          parentid    sname      
----------- ----------- ---------- 
7           3           节点6
7           6           节点7

（所影响的行数为 2 行）
*/

------解决方案--------------------

-- sql 2005 可以直接查询
SQL code
;WITH
TREE AS(
    SELECT * FROM T
    WHERE parentid = 3  -- 要查询的父 id
    UNION ALL
    SELECT T * FROM T, TREE
    WHERE T.parentid = TREE.id
)
SELECT * FROM TREE