SQL递归函数列出父级的所有子级(ID ParentID模式)

--调用方法：

--select * from GetChild('24')

--select id from GetChild('24')

--select * from KuCun where ProductType in(select id from GetChild('24'))

Create

function
[dbo].[GetChild](@ID
varchar
(10))

returns
@t
table
(ID
varchar
(10),ParentID
varchar
(10),
Level

int
)

as

begin

declare
@i
int

set
@i = 1

insert

into
@t
select
@ID,@ID,0
--当前级，本级，如果不要的话可以注释掉或再加个参数来选择操作

insert

into
@t
select
ID,ParentID,@i
from
Dept
where
ParentID = @ID

while @@rowcount<>0

begin

set
@i = @i + 1

insert

into
@t

select

a.ID,a.ParentID,@i

from

Dept a,@t b

where

a.ParentID=b.ID and
b.
Level
= @i-1

end

return

end

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

--在SQL Server2005中其实提供了CTE[公共表表达式]来实现递归:

Declare
@Id
Int

Set
@Id = 24;
---在此修改父节点

With
RootNodeCTE(Id,ParentId)

As

(

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

Union

All

Select
Dept.Id,Dept.ParentId
From
RootNodeCTE

Inner

Join
Dept

On
RootNodeCTE.Id = Dept.ParentId

)

Select
*
From
RootNodeCTE

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

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

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

--生成测试数据

create

table
Dept(ID
int
,ParentID
int
,msg
varchar
(20))

insert

into
Dept
select
1,0,
null

insert

into
Dept
select
2,1,
null

insert

into
Dept
select
3,1,
null

insert

into
Dept
select
4,2,
null

insert

into
Dept
select
5,3,
null

insert

into
Dept
select
6,5,
null

insert

into
Dept
select
7,6,
null

go

--创建用户定义函数

Create

function
[dbo].[GetChild](@ID
varchar
(10))

returns
@t
table
(ID
varchar
(10),ParentID
varchar
(10),
Level

int
)

as

begin

declare
@i
int

set
@i = 1

insert

into
@t
select
@ID,@ID,0
--当前级，本级，如果不要的话可以注释掉或再加个参数来选择操作

insert

into
@t
select
ID,ParentID,@i
from
Dept
where
ParentID = @ID

while @@rowcount<>0

begin

set
@i = @i + 1

insert

into
@t

select

a.ID,a.ParentID,@i

from

Dept a,@t b

where

a.ParentID=b.ID and
b.
Level
= @i-1

end

return

end

--执行查询

select
ID
from
dbo.GetChild(3)

go

--输出结果

/*

3

5

6

7

*/

--删除测试数据

drop

function
GetChild

drop

table
Dept