rails d migration code example

Example 1: rails rollback multiple migrations

rake db:rollback STEP=n 
# n = how many migrations you want to rollback

Example 2: how create migration rails

rails g migration AddPartNumberToProducts

Example 3: rails g migration add columns

$ rails generate migration AddDetailsToProducts part_number:string price:decimal

Example 4: activerecord add column

class AddPartNumberToProducts < ActiveRecord::Migration[6.0]
  def change
    add_column :products, :part_number, :string
  end
end

Example 5: rials db down

bin/rails db:migrate:down VERSION=YYYYMMDDHHMMSS