How to change DATABASE_URL for a heroku application

Question

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 attachm

Answer 1

After trying out most these answers, I came across an update in 2016, here: the database needs to be detached first, then update the variable of the DATABASE_URL.

heroku addons:attach heroku-postgresql -a  --as HEROKU_DATABASE
heroku addons:detach DATABASE -a 
heroku config:add DATABASE_URL=