Unable to execute a SELECT / UNION ALL in the SWQL Studio

Hello,

I'm not able to execute the following SELECT / UNION query in the SWQL Studio:

select TimeStamp, NodeID, InterfaceIDRx, Port, SourceIP, DestinationIP, IngressBytes, protocolID

from Orion.Netflow.Flows

where InterfaceIDRx = 917

  and TimeStamp >= '2014.12.17 19:10:00'

  and TimeStamp <  '2014.12.17 19:11:00'

UNION ALL

select TimeStamp, NodeID, InterfaceIDTx, Port, SourceIP, DestinationIP, EgressBytes, protocolID

from Orion.Netflow.Flows

where InterfaceIDTx = 917

  and TimeStamp >= '2014.12.17 19:10:00'

  and TimeStamp <  '2014.12.17 19:11:00'

Error: mismatched input 'select' expecing '('

Could you please provide me the right syntax?

Thanks a lot

Livio