在数据库中表示文件系统(在SQL Server 2008中使用hierarchyid)

Question

我还没有找到任何具体的例子，但我对使用hierarchyid数据类型表示具有更新等的整个目录结构感兴趣。这是一个常见的用例引用的hierarchyid，但我找不到任何文章构建这样的例子。

我只想表示一个完整的目录结构，例如:

/dir1
/file1
/dir2
/dir2/dir3
/dir2/dir3/file2

**我没有尝试将此文件系统与磁盘上的文件系统同步。它纯粹通过数据库表示。* *

Answer 1

下面是一个通过hierarchyid表示文件系统的示例:

/*
Setup:
 - Create the table to hold the files
 - nodeDepth is identifier of the depth for readability
 - fullpath is the full path of the file or directory
 - nodePath is the HierarchyID
 - nodePath identifies the row within the tree
*/
DECLARE @t TABLE (
  nodeID INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
  nodeDepth VARCHAR(10) NOT NULL,
  fullPath VARCHAR(20) NOT NULL,
  nodePath HIERARCHYID NOT NULL
) 

Load data:

/*
Load the nodePath value with the Parse command: 
 - The root node has a single /
 - Every nodePath must begin and end with /
 - /1/2/ the second item on level 2
*/
INSERT @t (fullPath, nodeDepth, nodePath) VALUES  
('/','1',HIERARCHYID::Parse('/')),
('/dir1','1.1',HIERARCHYID::Parse('/1/1/')),
('/file1','1.2',HIERARCHYID::Parse('/1/2/')),
('/dir2','1.3',HIERARCHYID::Parse('/1/3/')),
('/dir2/dir3','1.3.1',HIERARCHYID::Parse('/1/3/1/')),
('/dir2/dir3/file2','1.3.1.1',HIERARCHYID::Parse('/1/3/1/1/'))

显示路径

SELECT *
FROM @t 
nodeID      nodeDepth  fullPath             nodePath
----------- ---------- -------------------- --------
1           1          /                    0x
2           1.1        /dir1                0x5AC0
3           1.2        /file1               0x5B40
4           1.3        /dir2                0x5BC0
5           1.3.1      /dir2/dir3           0x5BD6
6           1.3.1.1    /dir2/dir3/file2     0x5BD6B0

获取file2的祖先文件(向上一级):

SELECT * 
FROM @t 
WHERE nodePath = 
  (SELECT nodePath.GetAncestor(1)
   FROM @t 
   WHERE fullPath = '/dir2/dir3/file2')
nodeID      nodeDepth  fullPath             nodePath
----------- ---------- -------------------- ---------
5           1.3.1      /dir2/dir3           0x5BD6

获取dir2的所有后代:

SELECT *
FROM @t 
WHERE nodePath.IsDescendantOf(
  (SELECT nodePath 
   FROM @t 
   WHERE fullPath = '/dir2')) = 1
AND fullPath <> '/dir2' /* Parent is considered its own descendant */
nodeID      nodeDepth  fullPath             nodePath
----------- ---------- -------------------- --------
5           1.3.1      /dir2/dir3           0x5BD6
6           1.3.1.1    /dir2/dir3/file2     0x5BD6B0

获取根路径:

SELECT * 
FROM @t 
WHERE nodePath = HIERARCHYID::GetRoot()
nodeID      nodeDepth  fullPath             nodePath
----------- ---------- -------------------- --------
1           1          /                    0x

获取file2的级别:

SELECT nodePath.GetLevel() AS level
FROM @t 
WHERE fullPath = '/dir2/dir3/file2'
level
------
4

引用:

• HierarchyID数据类型介绍
SQL Server 2008中的HierarchyID数据类型
• hierarchyid (transact - sql)