Active Record Migrations Intro

Active Record includes a migration system that allows developers to version-control database schema changes. Migrations are written in Ruby and provide a way to evolve the database schema over time.

The migration files are located in the db/migrate directory. Migration files are usually generated using the rails g migration command.

Example:

rails g migration CreateUsers name:string age:integer

Generates a file named db/migrate/YYYYMMDDHHMMSS_create_users.rb.

class CreateUsers < ActiveRecord::Migration[7.1]
  def change
    create_table :users do |t|
      t.string :name
      t.integer :age
    end
  end
end