What are some examples of Rails migrations?

What are some examples of Rails migrations?

Rails migrations are used to modify your database schema over time. Here are a few examples:

1. Creating a new table:

   class CreateUsers < ActiveRecord::Migration[6.0]
     def change
       create_table :users do |t|
         t.string :name
         t.string :email
         t.timestamps
       end
     end
   end
   

2. Adding a column to an existing table:

   class AddAgeToUsers < ActiveRecord::Migration[6.0]
     def change
       add_column :users, :age, :integer
     end
   end
   

3. Removing a column:

   class RemoveAgeFromUsers < ActiveRecord::Migration[6.0]
     def change
       remove_column :users, :age
     end
   end
   

Would you like to see more examples or details on a specific migration?

Can you explain how to roll back a migration?

Certainly! To roll back a migration in Rails, you can use the command:

rails db:rollback

This command will undo the last migration that was run. If you want to roll back multiple migrations, you can specify the number of steps:

rails db:rollback STEP=3

This will roll back the last three migrations. You can also use the db:migrate:down command with the migration version to roll back a specific migration.

What if I want to run a migration without affecting the production database?

If you want to run migrations without affecting the production database, you can use the RAILS_ENV environment variable to specify a different environment, like development or test. For example:

RAILS_ENV=test rails db:migrate

This command will run the migrations in the test environment instead of production. Always ensure you are in the correct environment before running migrations!