title: Postgres database create if not exists
body: <p>Is there an analog to <code>CREATE TABLE IF NOT EXISTS</code> for creating databases? </p>
  
  <p>Background: I am writing a script to automatically set up the schema in PostgreSQL on an unknown system. I am not sure if the database (or even part of the schema) was already deployed, so I want to structure my code to not fail (or ideally even show errors) if some of the structure already exists. I want to differentiate the errors that prevent me from creating a database (so abort future schema changes since they will not work) from this error.</p>