Many of us are guilty of saying “database” when we mean a database server or a DBMS. A database is a collection of tables storing related data, schemas, stored procs, and per­mis­sions. Most database servers are capable of managing many databases si­mul­ta­ne­ous­ly.

I needed to create a new PostgreSQL database at Amazon’s RDS last week. I already had an RDS instance; I needed a new database on that instance. My Google searches turned up various recipes for creating a new RDS instance.

The following worked for me:

• SSH to an EC2 instance inside our VPC, so that I could connect to the RDS instance using psql.
• Then run:

psql --host=SOME-DBMS-HOST --dbname EXISTING_DB \
     --username=YOUR-USERNAME --password \
     --command="CREATE DATABASE new_database WITH OWNER some_owner"

• Using --password will prompt you for a password. If you’ve set up ~/.pgpass, you can specify --no-password instead.
• The critical part that was hard to figure out is that I had to specify --dbname EX­IST­ING_DB. Otherwise, psql kept trying to connect to a database called YOUR-USERNAME.
• This should work for any PostgreSQL server, not just one hosted at RDS.