There is no way to query a database other than the current one. Because PostgreSQL loads database-specific system catalogs, it is uncertain how a cross-database query should even behave. contrib/dblink allows cross-database queries using function calls.
How do I connect two databases in PostgreSQL?
- Install the extension.
- Create a foreign server.
- Create an user mapping (so that different users could do be allowed to perform different operations on the remote tables)
- Define foreign tables by specifying columns yourself or importing whole tables/schemas automatically (9.5+)
Can you have multiple database in PostgreSQL?
It is not possible to access more than one database per connection. (But an application is not restricted in the number of connections it opens to the same or other databases.) Databases are physically separated and access control is managed at the connection level.
