UPDATE t_node_agent t 
SET t.is_duplicate = 1 
WHERE
	t.flag = 1 
	AND t.f_hostname IN (
	SELECT
		* 
	FROM
	( SELECT tt.f_hostname FROM t_node_agent tt WHERE tt.f_flag = 1 GROUP BY tt.f_hostname HAVING count( f_hostname ) > 1 ) result 
	)