I know this isn't exactly what you are asking, but it is an example I am using to combine data from two different tables: nodesdata and apm-hardwareinfo. This helped to aggregate my serial numbers with my IP and SNMP location information to be used for some inventory purposes.
select nodesdata.caption, nodesdata.IP_Address, apm_hardwareinfo.model, apm_hardwareinfo.servicetag, nodesdata.location
from nodesdata, apm_hardwareinfo
where nodesdata.nodeid = apm_hardwareinfo.nodeid
order by caption asc
You may still end up with two serial columns, one for Juniper and one for not.
Hope this helps some.