Question

我需要在SQL Server 2005上实现一个多父树（或有向图）。我已经阅读了几篇文章，但大多数文章使用的是具有独特根的单个父树，如下所示。

-My PC
   -Drive C
      -Documents and Settings
      -Program Files
         -Adobe
         -Microsoft
      -Folder X
   -Drive D
      -Folder Y
      -Folder Z

在这一个中，一切都来自根元素（我的PC）。

在我的情况下，一个孩子可以拥有多于一个父母，如下所示：

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

返回以下SET：

Id                   NextId
-------------------- --------------------
A                    B
B                    C
B                    X
C                    E
C                    D
D                    F
E                    F

预期结果SET：

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（对我来说也不起作用，因为我从一开始就不知道根对象）并使用A作为起点将忽略G-> B关系。

所以，这个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SINGLE-parent树中很明显（永远是根对象）。但是在多父树中，您可以拥有多个“根”对象（如示例中所示，G和A是“根”对象，其中root是没有父（祖先）的对象）。

所以我有点被困在这里...我需要修改查询，不要求一个起始对象，并递归遍历整个树。我不知道（Id，NextId）实现是否可能......我可能需要使用某种关联矩阵，邻接矩阵或其他任何东西（见http://willets.org/sqlgraphs.html）将其存储为图形。 / p>

有任何帮助吗？你们觉得怎么样？非常感谢你的时间=）

干杯！

来源： Source 1 Source 2 Source 3

Answer 1

好吧，我终于提出了以下解决方案。这是我发现支持多根树和循环图的方式。

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

对某些人有用。对我来说= P 感谢

Answer 2

如果要将所有根对象用作起始对象，则应首先更新数据以包含有关根对象（和叶子）的信息。您应该添加以下插入内容：

insert into #ObjectRelations values (NULL, 'G')
insert into #ObjectRelations values (NULL, 'A')
insert into #ObjectRelations values ('X', NULL)
insert into #ObjectRelations values ('F', NULL)

当然，您也可以编写锚点查询，以便选择Id不会出现NextId的记录作为根节点，但这更容易。< / p>

接下来，修改您的锚点查询，如下所示：

SELECT rel.Id,
       rel.NextId
FROM #ObjectRelations rel
WHERE rel.Id IS NULL

如果你运行这个查询，你会发现你得到了很多重复，很多次出现了很多弧。这是因为您现在有两个来自锚点查询的结果，因此树遍历了两次。

这可以通过将select语句更改为此来修复（请注意DISTINCT）：

SELECT DISTINCT o.*
FROM   Objects o

Answer 3

如果你不想做罗纳德建议的插入，那就行了！

WITH CTE_MultiParent  (ID, ParentID) 
AS 
(
    SELECT ID, ParentID FROM #ObjectRelations
    WHERE ID NOT IN 
    (
        SELECT DISTINCT ParentID FROM #ObjectRelations
    )
    UNION ALL
    SELECT ObjR.ID, ObjR.ParentID FROM #ObjectRelations ObjR INNER JOIN CTE_MultiParent
    ON CTE_MultiParent.ParentID = ObjR.Id
)

SELECT DISTINCT * FROM CTE_MultiParent

多父树（或有向图）实现sql server 2005

3 个答案: