多父树(或有向图)实现 sql server 2005 [英] Multiple parents tree (or digraph) implementation sql server 2005
问题描述
我需要在 SQL Server 2005 上实现一个多父树(或有向图).我读过几篇文章,但其中大部分都使用具有唯一根的单亲树,如下所示.
I need to implement a multi-parented tree (or digraph) onto SQL Server 2005. I've read several articles, but most of them uses single-parented trees with a unique root like the following one.
-My PC
-Drive C
-Documents and Settings
-Program Files
-Adobe
-Microsoft
-Folder X
-Drive D
-Folder Y
-Folder Z
在这一个中,一切都来自一个根元素(我的电脑).
In this one, everything derives from a root element (My PC).
在我的例子中,一个孩子可以有多个父母,如下所示:
In my case, a child could have more than 1 parent, like the following:
G A
/
B
/
X C
/
D E
/
F
所以我有以下代码:
create table #ObjectRelations
(
Id varchar(20),
NextId varchar(20)
)
insert into #ObjectRelations values ('G', 'B')
insert into #ObjectRelations values ('A', 'B')
insert into #ObjectRelations values ('B', 'C')
insert into #ObjectRelations values ('B', 'X')
insert into #ObjectRelations values ('C', 'E')
insert into #ObjectRelations values ('C', 'D')
insert into #ObjectRelations values ('E', 'F')
insert into #ObjectRelations values ('D', 'F')
declare @id varchar(20)
set @id = 'A';
WITH Objects (Id, NextId) AS
( -- This is the 'Anchor' or starting point of the recursive query
SELECT rel.Id,
rel.NextId
FROM #ObjectRelations rel
WHERE rel.Id = @id
UNION ALL -- This is the recursive portion of the query
SELECT rel.Id,
rel.NextId
FROM #ObjectRelations rel
INNER JOIN Objects -- Note the reference to CTE table name (Recursive Join)
ON rel.Id = Objects.NextId
)
SELECT o.*
FROM Objects o
drop table #ObjectRelations
<小时>
返回以下 SET:
Which returns the following SET:
Id NextId
-------------------- --------------------
A B
B C
B X
C E
C D
D F
E F
预期结果集:
Id NextId
-------------------- --------------------
G B
A B
B C
B X
C E
C D
D F
E F
请注意,关系 G->B 缺失,因为它要求一个起始对象(这对我也不起作用,因为我从一开始就不知道根对象)并使用 A 作为开始point 将忽略 G->B 关系.
Note that the relation G->B is missing, because it asks for an starting object (which doesn't work for me also, because I don't know the root object from the start) and using A as the start point will ignore the G->B relationship.
因此,此代码在我的情况下不起作用,因为它要求一个起始对象,这在单父树中很明显(将始终是根对象).但是在多父树中,您可能有 1 个以上的根"对象(就像在示例中一样,G 和 A 是根"对象,其中根是一个没有父(祖先)的对象).
So, this code doesn't work in my case because it asks for a starting object, which is obvious in a SINGLE-parent tree (will always be the root object). But in multi-parent tree, you could have more than 1 "root" object (like in the example, G and A are the "root" objects, where root is an object which doesn't have a parent (ancestor)).
所以我有点卡在这里...我需要修改查询以不要求起始对象并递归遍历整个树.我不知道 (Id, NextId) 实现是否可行...可能是我需要使用某种发生率矩阵、邻接矩阵或其他方式将它存储为图形(参见 http://willets.org/sqlgraphs.html).
So I'm kind of stucked in here... I need to modify the query to NOT ask for a starting object and recursively traverse the entire tree. I don't know if that's possible with the (Id, NextId) implementation... may be I need to store it like a graph using some kind of Incidence matrix, adjacency matrix or whatever (see http://willets.org/sqlgraphs.html).
有什么帮助吗?你们觉得怎么样?非常感谢您的时间=)
Any help? What do you think guys? Thank you very much for your time =)
干杯!
推荐答案
好吧,我终于想出了以下解决方案.这是我发现支持多根树和循环有向图的方式.
Well, I finally came up with the following solution. It's the way I found to support multi-root trees and also cycling digraphs.
create table #ObjectRelations
(
Id varchar(20),
NextId varchar(20)
)
/* Cycle */
/*
insert into #ObjectRelations values ('A', 'B')
insert into #ObjectRelations values ('B', 'C')
insert into #ObjectRelations values ('C', 'A')
*/
/* Multi root */
insert into #ObjectRelations values ('G', 'B')
insert into #ObjectRelations values ('A', 'B')
insert into #ObjectRelations values ('B', 'C')
insert into #ObjectRelations values ('B', 'X')
insert into #ObjectRelations values ('C', 'E')
insert into #ObjectRelations values ('C', 'D')
insert into #ObjectRelations values ('E', 'F')
insert into #ObjectRelations values ('D', 'F')
declare @startIds table
(
Id varchar(20) primary key
)
;WITH
Ids (Id) AS
(
SELECT Id
FROM #ObjectRelations
),
NextIds (Id) AS
(
SELECT NextId
FROM #ObjectRelations
)
INSERT INTO @startIds
/* This select will not return anything since there are not objects without predecessor, because it's a cyclic of course */
SELECT DISTINCT
Ids.Id
FROM
Ids
LEFT JOIN
NextIds on Ids.Id = NextIds.Id
WHERE
NextIds.Id IS NULL
UNION
/* So let's just pick anyone. (the way I will be getting the starting object for a cyclic doesn't matter for the regarding problem)*/
SELECT TOP 1 Id FROM Ids
;WITH Objects (Id, NextId, [Level], Way) AS
( -- This is the 'Anchor' or starting point of the recursive query
SELECT rel.Id,
rel.NextId,
1,
CAST(rel.Id as VARCHAR(MAX))
FROM #ObjectRelations rel
WHERE rel.Id IN (SELECT Id FROM @startIds)
UNION ALL -- This is the recursive portion of the query
SELECT rel.Id,
rel.NextId,
[Level] + 1,
RecObjects.Way + ', ' + rel.Id
FROM #ObjectRelations rel
INNER JOIN Objects RecObjects -- Note the reference to CTE table name (Recursive Join)
ON rel.Id = RecObjects.NextId
WHERE RecObjects.Way NOT LIKE '%' + rel.Id + '%'
)
SELECT DISTINCT
Id,
NextId,
[Level]
FROM Objects
ORDER BY [Level]
drop table #ObjectRelations
可能对某人有用.这是给我的=P谢谢
Could be useful for somebody. It is for me =P Thanks
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