Join between Postgis table and Postgresql table

[Carlo Calvino]

Hello all of you,
I built a spatial database with PostgreSql/PostGis, and imported a
shapefile (cities.shp) inside it. So I have a postgresql database with 2
tables, one for the geographic data and the other for alphanumeric data.
I was able to publish the vector data by MapServer, and I was also able to
query it correctly. But...what about querying the vector layer using
information from the second table? I need joining the two tables. As far
as I know, it is only possible a join between Postgis and a dbf file, not
a DBMS. So there are any suggestions?