SQL: Recursive Path

Question

Is it possible to create a "tree resolver" in SQL?

I have a table:

ID Name Parent
1  a
2  b    1
3  c    1
4  d    3

Now I want a SQL query that returns:

ID   PATH
1    /a
2    /a/b
3    /a/c
4    /a/c/d

Is this possible with SQL? It would make many things easier for me. Any help would really be appreciated!

Answer 1

Using CTE in sql server 2005 and later, here's a snippet that I have to do this:

WITH Paths([Level], [FullPath], [ID]) AS 
(
    SELECT 
        0 AS [Level], 
        Name AS FullPath, 
        ID
    FROM dbo.Entity
    WHERE (ParentEntityID IS NULL)

    UNION ALL

    SELECT 
        p.[Level] + 1 AS [Level], 
        CASE RIGHT(p.[FullPath], 1) 
        WHEN '\' THEN p.[FullPath] + c.[Name] 
        ELSE p.[FullPath] + '\' + c.[Name] 
    END AS FullPath, 
    c.ID
    FROM dbo.Entity AS c 
    INNER JOIN Paths AS p ON p.ID = c.ParentEntityID
)
SELECT [FullPath], [ID]
FROM Paths