获取文件夹的树结构答案

【问题标题】：Get tree structure of folders获取文件夹的树结构
【发布时间】：2010-10-05 22:30:10
【问题描述】：

我的数据库中的“文件夹”表中有以下文件夹：

文件夹 1
文件夹2
文件夹 3
文件夹 4

文件夹路径 - Folder1\Folder2\Folder3\Folder4

当我点击 Folder3 时，我必须将路径设置为 - Folder1\Folder2\Folder3。为此，我传递的是 Folder3 的 folderID。

我怎样才能得到这个结果？

表结构

FolderiD 文件夹名称 ParentID

1 文件夹 1 0

2 文件夹 2 1

3 文件夹3 2

4 文件夹4 3

【问题讨论】：

这与 SQL Server 有什么关系？
sql server 和文件夹之间有什么关系？
表folders的结构是什么？

标签： sql-server

【解决方案1】：

这是我在这里重复这个问题时给出的答案：How to query hierarchical information with SQL-Server 2000?

/* Set up test data */
create table Folders (
    FolderID int,
    FolderName varchar(10),
    ParentID int
)

insert into Folders
    (FolderID, FolderName, ParentID)
    select 1,'Folder1',0 union all
    select 2,'Folder2',1 union all
    select 3,'Folder3',2 union all
    select 4,'Folder4',3        
go

/* Create function */
create function dbo.CreateFolderPath (@FolderID int)
returns varchar(1000)
as
begin
    declare @ParentID int
    declare @FolderPath varchar(1000)
    set @FolderPath = ''

    select @ParentID = ParentID
        from Folders
        where FolderID = @FolderID

    while @ParentID<>0 begin
        select @FolderPath = FolderName + '\' + @FolderPath, @ParentID = ParentID
            from Folders
            where FolderID = @ParentID
    end /* while */

    return @FolderPath
end /* function */
go

/* Demo the function */
select dbo.CreateFolderPath(4)

/* Clean up after demo */
drop function dbo.CreateFolderPath
drop table Folders

【讨论】：

【解决方案2】：

您可以为此使用递归 CTE。

/*Test Data*/
SELECT *
INTO #Folders FROM 
(SELECT 1 AS FolderId, 0 AS ParentId, 'Folder1' AS FolderName UNION ALL
SELECT 2 AS FolderId, 1 AS ParentId, 'Folder2' AS FolderName UNION ALL
SELECT 3 AS FolderId, 2 AS ParentId, 'Folder3' AS FolderName UNION ALL
SELECT 4 AS FolderId, 3 AS ParentId, 'Folder4' AS FolderName ) F


/*Query*/    
;WITH fl AS
     ( SELECT 1 AS Level,
             FolderId   ,
             ParentId   ,
             FolderName ,
             CAST(FolderName AS nvarchar(MAX)) AS F
     FROM    #Folders
     WHERE   FolderId = 3

     UNION ALL

     SELECT Level +1    ,
            f.FolderId  ,
            f.ParentId  ,
            f.FolderName,
            CAST(f.FolderName + '/' + fl.F AS nvarchar(MAX))
     FROM   fl
            JOIN #Folders f
            ON     fl.ParentId = f.FolderId
     )
SELECT   top (1) F
FROM     fl
ORDER BY Level DESC

drop table #Folders

【讨论】：

@Adu - 不。您需要为此使用 WHILE 循环或递归调用表值函数。