title: How to change DATABASE_URL for a heroku application
body: <p>I wanted to use an external Database with my heroku application. But I'm unable to edit the configuration cariables. I tried using GUI, Which says, Cannot overwrite attachment values DATABASE_URL. While I tried using CLI as well. I used the command: <code>heroku config:addDATABASE_URL="postgresql://username:password@IP:PORT"</code>. However, this throws an error <code>... is not a heroku command.</code></p>