A federated query is one that
accesses data from multiple data sources and returns a single result
set. The data remains stored in the data source. For example, in
this query, data is requested from an Oracle table and from two Teradata
tables:
select Ora1.city Ora1.State, Ora1.zip
from Oracle.Tbl1 Ora1, Teradata.Tbl2 Tera2, Teradata.Tbl3 Tera3
where Ora1.zip = Tera2.zip and Tera2.zip = Tera3.zip;