DECLARE	@Sample TABLE
	(
		ParentID CHAR(10) NOT NULL,
		ChildID CHAR(10) NOT NULL
	)

INSERT	@Sample
VALUES	('0000000000', '0000000001'),
	('0000000000', '0000000124'),
	('0000000000', '0000007953'),
	('0000007953', '0000007954'),
	('0000007954', '0000007955'),
	('0000007954', '0000007956'),
	('0000007957', '0000007958'),
	('0000007958', '0000007959'),
	('0000007958', '0000007960'),
	('0000007958', '0000007961')

;WITH cteSource(ParentID, ChildID, PathID, Iteration)
AS (
	SELECT DISTINCT	CAST(NULL AS CHAR(10)) AS ChildID,
			ParentID,
			CAST('/' + ChildID AS VARCHAR(MAX)) AS PathID,
			CAST(0 AS INT) AS Iteration
	FROM		@Sample
 
	UNION ALL

	SELECT		s.ParentID,
			s.ChildID,
			c.PathID + '/' + CAST(s.ChildID AS VARCHAR(MAX)) AS PathID,
			c.Iteration + 1 AS Iteration
	FROM		cteSource AS c
	INNER JOIN	@Sample AS s ON s.ParentID = c.ChildID
)
SELECT		REPLICATE('-', 10 * Iteration) + ChildID
FROM		cteSource
GROUP BY	REPLICATE('-', 10 * Iteration) + ChildID
ORDER BY	MIN(PathID)