SQL Recursion: Get the main state off of a sub state - sql

Question

I found this nice example of SQL recursion with a CTE, but fail to apply it to my table:
http://walkingoncoals.blogspot.de/2009/12/fun-with-recursive-sql-part-1.html
I have the following table (ObjectStates):
ID Title ParentID
1 Draft null
2 Green null
3 Red null
4 Foo 1
5 Bar 4
I am trying to create a function which returns the "main" state when queried. Example:
GetMainState(5)
-- Shall return 1
GetMainState(4)
-- Shall return 1
GetMainState(2)
-- Shall return 2
I have so far:
CREATE FUNCTION [dbo].[GetMainObjectState] (#ObjectStateID INT)
RETURNS TABLE
AS
RETURN
(
WITH StateRecurcsion(ID, ParentID, Level) AS
(
SELECT ID, ParentID, 0
FROM ObjectStates
WHERE ID = #ObjectStateID
UNION ALL
SELECT uOS.ID, uOS.ParentID, sOS.Level+1
FROM ObjectStates uOS, StateRecurcsion sOS
WHERE uOS.ParentID= sOS.ID
)
SELECT os.ID, os.Title, sos.Level
FROM ObjectStates os, StateRecurcsion sos
WHERE os.ID = sos.ID
)
GO
I tried to create the function just as in the tutorial shown above, but somehow I'm not getting the correct results.

Answer 1

You could create a CTE containing a "root" value and then query it within your function e.g.:
;WITH CTEHierarchy
AS (
SELECT
ID
,0 AS LEVEL
,ID AS root
FROM ObjectStates
WHERE ParentID IS NULL
UNION ALL
SELECT
ObjectStates.ID
,LEVEL + 1 AS LEVEL
,[root]
FROM ObjectStates
INNER JOIN CTEHierarchy uh ON uh.id = ObjectStates.ParentID
)
SELECT [root]
FROM CTEHierarchy
WHERE ID = #ObjectStateID