Oracle: check the existance of logon/logoff triggers

SELECT 
 DECODE((COUNT(trigger_name)),0,'LOGON trigger missing', 
 'Number of logon triggers: ' || COUNT(trigger_name) ) "INFO"
FROM sys.dba_triggers
WHERE 
 TRIGGERING_EVENT LIKE 'LOGON%' 
 AND status='ENABLED' 
 AND owner='SYS'
UNION
SELECT 
 DECODE((COUNT(trigger_name)),0,'LOGOFF trigger missing','', 
 'Number of logoff triggers:' || COUNT(trigger_name)) "INFO"
FROM sys.dba_triggers
WHERE 
 TRIGGERING_EVENT LIKE 'LOGOFF%' 
 AND status='ENABLED' 
 AND owner='SYS'