Si CREATIONDATE es un tipo de datos de fecha, contiene el elemento de tiempo hasta segundos. Es muy poco probable que el Id. de incidente que está buscando tenga la hora exacta. Formatee la fecha a una fecha ISO y GROUP BY ignorará las diferencias horarias.
SELECT TO_CHAR(MIN(I.INCIDENTID)) AS "Incident ID",
to_char(I.CREATIONDATE, 'yyyy-mm-dd') AS "Creation Date",
M.MESSAGESUBJECT AS "Email Subject",
MO.IPADDRESS AS "IP Address",
MO.DOMAINUSERNAME AS "Login ID",
MO.ENDPOINTMACHINENAME AS "Computer Name"
FROM MESSAGE M
LEFT JOIN INCIDENT I
ON M.MESSAGESOURCE = I.MESSAGESOURCE
AND M.MESSAGEID = I.MESSAGEID
AND M.MESSAGEDATE = I.MESSAGEDATE
LEFT JOIN MESSAGEORIGINATOR MO
ON M.MESSAGEORIGINATORID = MO.MESSAGEORIGINATORID
LEFT JOIN MESSAGEEXT ME
ON ME.MESSAGEID = M.MESSAGEID
LEFT JOIN INCIDENTSTATUS S
ON S.INCIDENTSTATUSID = I.INCIDENTSTATUSID
LEFT JOIN CUSTOMATTRIBUTESRECORD C
ON C.CUSTOMATTRIBUTESRECORDID = I.CUSTOMATTRIBUTESRECORDID
GROUP BY to_char(I.CREATIONDATE, 'yyyy-mm-dd')
M.MESSAGESUBJECT,
MO.IPADDRESS,
MO.DOMAINUSERNAME,
MO.ENDPOINTMACHINENAME
