WITH tbl (E_ID , PARENTID) AS (
	SELECT 1, NULL UNION ALL 
	SELECT 2, 1    UNION ALL 
	SELECT 3, 2    UNION ALL 
	SELECT 4, 2    UNION ALL 
	SELECT 5, NULL UNION ALL 
	SELECT 6, 5    UNION ALL 
	SELECT 7, 5    UNION ALL 
	SELECT 8, 7  
)
, tmpT (FirstID , E_ID , PARENTID) AS ( 
	SELECT E_ID , E_ID , PARENTID  FROM tbl WHERE PARENTID IS NULL
	UNION ALL 
	SELECT A.FirstID , R.E_ID , R.PARENTID  FROM tmpT A JOIN tbl R ON A.E_ID = R.PARENTID 
) 

SELECT 
	FirstID , E_ID , PARENTID
FROM tmpT 
ORDER BY FirstID , E_ID