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'