Hi ,
I had gone through the query, its returning the error when the timestamp is added in the select is because you missed the timestamp in the GROUP BY
If the same is added in the query it shall work
SELECT TOP 3 f.TimeStamp, f.SourceIP, f.DestinationIP, SUM(f.Bytes) as TotalBytes FROM Orion.Netflow.FlowsByConversation f
WHERE f.TimeStamp >= '2014-06-12 13:00:00' AND f.TimeStamp <= '2014-06-12 13:59:59'
AND InterfaceIDTx = 12060
GROUP BY f.SourceIP, f.DestinationIP,f.TimeStamp
ORDER BY SUM(f.Bytes) DESC
Cheers