Number rows in SQL Server using CTE

gistfile1.sql

;WITH T AS (
	SELECT 
		STEPNO,
		Row_Number() OVER (PARTITION BY JOBNAME ORDER BY STEPNO) AS RN
		FROM STEP
		WHERE BR = '00'
	)
UPDATE T
	SET
		STEPNO = RN

SELECT * FROM STEP WHERE BR = '00' ORDER BY JOBNAME, STEPNO