What are some examples of Rails migrations?

What are some examples of Rails migrations?

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

1. Creating a 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:

   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 following command in your terminal:

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 if you want to roll back a specific migration.

What if I want to apply a migration again after rolling it back?

After rolling back a migration, you can reapply it using the following command:

rails db:migrate

This will run all pending migrations, including the one you just rolled back. If you want to apply a specific migration, you can use:

rails db:migrate:up VERSION=your_migration_version

Replace your_migration_version with the version number of the migration you want to apply.