Support for cross database queries in Azure DB for postgres server

If you disabled "Deny public network access" & and enabled "Allow access to other Azure resources" under "Connection security" in your Azure Postgres server, you can use the dblink extension:

CREATE EXTENSION dblink;

SELECT dblink_connect('[connection_alias]','host=[azure_pg_hostname] port=5432
dbname=[other_db_name] user=[username]@[azure_pg_hostname] password=[password] sslmode=require');

SELECT * FROM dblink('[connection_alias]', 'select [field1], [field2] from public.[remote_table_name]') 
AS t([field1] [data type], [field2] [data type]);

or the foreign data wrapper extension:

CREATE EXTENSION postgres_fdw;

CREATE SERVER [connection_alias]
FOREIGN DATA WRAPPER postgres_fdw  
OPTIONS (host '[azure_pg_hostname]', dbname '[other_db_name]', port '5432');

CREATE USER MAPPING FOR ([user_name] | CURRENT_USER)
SERVER [connection_alias]
OPTIONS (user '[user_name]@[azure_pg_hostname]', password '[password]');

CREATE FOREIGN TABLE [local_table_name] ( 
[field1] [data type], [field2] [data type]
)
SERVER [connection_alias]
OPTIONS (schema_name 'public', table_name '[remote_table_name]');

SELECT * from [local_table_name];