Rebuild Umbraco's level/node structure after modifying parentids. Needs a better recursive union. This example only works with content types specifically.

update.sql

WITH CT AS (
	SELECT    *
	FROM      umbracoNode
	WHERE     (nodeObjectType = 'A2CB7800-F571-4787-9638-BC48539A0EFB') 
),
L1 AS (
	SELECT *, 1 'NewLevel', CAST(parentID as varchar) + ',' + CAST(id as varchar) 'NewPath'
	FROM CT
	WHERE parentID = -1
), L2 AS (
	SELECT CT.*, 2 'NewLevel', CAST(L1.NewPath as varchar) + ',' + CAST(CT.id as varchar) 'NewPath'
	FROM CT JOIN L1 
		ON CT.parentID = L1.id
), L3 AS (
	SELECT CT.*, 3 'NewLevel', CAST(L2.NewPath as varchar) + ',' + CAST(CT.id as varchar) 'NewPath'
	FROM CT JOIN L2
		ON CT.parentID = L2.id
), L4 AS (
	SELECT CT.*, 4 'NewLevel', CAST(L3.NewPath as varchar) + ',' + CAST(CT.id as varchar) 'NewPath'
	FROM CT JOIN L3
		ON CT.parentID = L3.id
), A as (

SELECT *
FROM L1
UNION 
SELECT *
FROM L2
UNION
SELECT *
FROM L3
UNION 
SELECT *
FROM L4
)

MERGE INTO umbracoNode U
USING A
  ON A.id = U.id
WHEN MATCHED THEN
  UPDATE
	SET U.level = A.newlevel,
		U.path = A.newpath;