RAILS_ENV is not working as expected. How to set the environment?

Question

I'm configuring a new app in rails5 on my localhost and am having some trouble establishing my environment. I set my environment variable to "development" but whenever I run rake db:drop it says the following

ActiveRecord::ProtectedEnvironmentError: You are attempting to run a destructive action against your 'production' database.
If you are sure you want to continue, run the same command with the environment variable:
DISABLE_DATABASE_ENVIRONMENT_CHECK=1

However my environment is set to development and not production:

sam$ printenv | grep RAILS_ENV
RAILS_ENV=development

What am I forgetting?

Many thanks for taking a look at this.

EDIT: My yaml looks like this

default: &default
  adapter: mysql2
  encoding: utf8
  username: ZZZZZZZ
  database: YYYYYYY
  host: 127.0.0.1
  socket: /tmp/mysql.sock
  password: XXXXXXXXX

development:
  <<: *default
  reconnect: true

Answer 1

You could set the environment using bin/rails db:environment:set RAILS_ENV=development

Answer 2

In case the DB you wanted to drop was a production copy, the ar_internal_metadata would hold the value production and rails db:drop throws the error you see. Running migrate changes the value to development

rails db:migrate
...
ActiveRecord::InternalMetadata Update (0.4ms)  UPDATE "ar_internal_metadata" SET "value" = $1, "updated_at" = $2 WHERE "ar_internal_metadata"."key" = $3  [["value", "development"]
...

Now you can drop db without error. No point on importing then dropping perhaps, but I got this error now after having played around with data in local rails console and wanted to drop and restore data.