SQL SERVER 2008 CTE生成结点的FullPath

       SQL SERVER 2008 使用CTE是经常的事儿，有时我们想存储一些冗余数据，像每个结点的FullPath。好的，现在来看如何生成FullPath:

DECLARE @tbl TABLE
  (
   Id int
  ,ParentId int
  )

INSERT  INTO @tbl
        ( Id, ParentId )
VALUES  ( 0, NULL )
,       ( 8, 0 )
,       ( 12, 8 )
,       ( 16, 12 )
,       ( 17, 16 )
,       ( 18, 17 )
,       ( 19, 17 )

;
WITH  abcd
        AS (
              -- anchor
            SELECT   id
                    ,ParentID
                    ,CAST(id AS VARCHAR(100)) AS [Path]
            FROM    @tbl
            WHERE   ParentId IS NULL
            UNION ALL
              --recursive member
            SELECT  t.id
                   ,t.ParentID
                   ,CAST(a.[Path] + ',' + CAST( t.ID AS VARCHAR(100)) AS varchar(100)) AS [Path]
            FROM    @tbl AS t
                    JOIN abcd AS a ON t.ParentId = a.id
           )
SELECT  Id ,ParentID ,[Path]
FROM    abcd
WHERE   Id NOT IN ( SELECT  ParentId
                    FROM    @tbl
                    WHERE   ParentId IS NOT NULL )

返回：

Id          ParentID    Path
----------- ----------- ----------------------
18          17          0,8,12,16,17,18
19          17          0,8,12,16,17,19

就这么简单，实际上有Sql server 2008中HierarchyType 也能很好的解决这个问题。我将在后面写一些关于HierarchyType的Post.

希望这篇POST对您有帮助。

Author Peter Liu http://wintersun.cnblogs.com