如何在 SQL 中生成通向给定节点的层次结构路径?
在我的 MS SQL 2008 R2 数据库中,我有这张表:
In my MS SQL 2008 R2 database I have this table:
TABLE [Hierarchy]
[ParentCategoryId] [uniqueidentifier] NULL,
[ChildCategoryId] [uniqueidentifier] NOT NULL
我需要编写一个查询来生成通向给定节点的所有路径.
I need to write a query that will generate all paths that lead to a given Node.
假设我有以下树:
A
-B
--C
-D
--C
这将被存储为:
NULL | A
A | B
A | D
B | C
D | C
当询问 C 的路径时,我想返回两条路径(或多或少这样写):
When asking for the Paths for C, I would like to get back two paths (written more or less like this):
A > B > C,
A > D > C
推荐答案
这是我的解决方案,Sql小提琴
DECLARE @child VARCHAR(10) = 'C'
;WITH children AS
(
SELECT
ParentCategoryId,
CAST(ISNULL(ParentCategoryId + '->' ,'') + ChildCategoryId AS VARCHAR(4000)) AS Path
FROM Hierarchy
WHERE ChildCategoryId = @child
UNION ALL
SELECT
t.ParentCategoryId,
list= CAST(ISNULL(t.ParentCategoryId + '->' ,'') + d.Path AS VARCHAR(4000))
FROM Hierarchy t
INNER JOIN children AS d
ON t.ChildCategoryId = d.ParentCategoryId
)
SELECT Path
from children c
WHERE ParentCategoryId IS NULL
输出:
A->D->C
A->B->C
<小时>
更新:
@AlexeiMalashkevich,要获取 id,你可以试试这个
@AlexeiMalashkevich, to just get id, you may try this
SQL 小提琴
DECLARE @child VARCHAR(10) = 'C'
;WITH children AS
(
SELECT
ParentCategoryId,
ChildCategoryId AS Path
FROM Hierarchy
WHERE ChildCategoryId = @child
UNION ALL
SELECT
t.ParentCategoryId,
d.ParentCategoryId
FROM Hierarchy t
INNER JOIN children AS d
ON t.ChildCategoryId = d.ParentCategoryId
)
SELECT DISTINCT PATH
from children c
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