Reset the database (purge all), then seed a database

I use rake db:reset which drops and then recreates the database and includes your seeds.rb file. http://guides.rubyonrails.org/migrations.html#resetting-the-database

You can delete everything and recreate database + seeds with both:

1. rake db:reset: loads from schema.rb
2. rake db:drop db:create db:migrate db:seed: loads from migrations

Make sure you have no connections to db (rails server, sql client..) or the db won't drop.

schema.rb is a snapshot of the current state of your database generated by:

rake db:schema:dump

As of Rails 5, the rake commandline tool has been aliased as rails so now

rails db:reset instead of rake db:reset

will work just as well

If you don't feel like dropping and recreating the whole shebang just to reload your data, you could use MyModel.destroy_all (or delete_all) in the seed.db file to clean out a table before your MyModel.create!(...) statements load the data. Then, you can redo the db:seed operation over and over. (Obviously, this only affects the tables you've loaded data into, not the rest of them.)

There's a "dirty hack" at https://stackoverflow.com/a/14957893/4553442 to add a "de-seeding" operation similar to migrating up and down...

on Rails 6 you can now do something like

rake db:seed:replant This Truncates tables of each database for current environment and loads the seeds

https://blog.saeloun.com/2019/09/30/rails-6-adds-db-seed-replant-task-and-db-truncate_all.html

$ rails db:seed:replant --trace
** Invoke db:seed:replant (first_time)
** Invoke db:load_config (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute db:load_config
** Invoke db:truncate_all (first_time)
** Invoke db:load_config
** Invoke db:check_protected_environments (first_time)
** Invoke db:load_config
** Execute db:check_protected_environments
** Execute db:truncate_all
** Invoke db:seed (first_time)
** Invoke db:load_config
** Execute db:seed
** Invoke db:abort_if_pending_migrations (first_time)
** Invoke db:load_config
** Execute db:abort_if_pending_migrations
** Execute db:seed:replant