Query two database at once

Hi,

I want to ewecute a query on two database like this :

SELECT * FROM table01 T1, table02 T2 WHERE T1.gid=T2.gid AND 
T2.my_field='".$value."'

The problem is that table01 is in a different database than table02 and 
i don't know how to telle postgresql
to look in two db.
Is there a solution other than execute two query ?
Thanks