Rails 3: How to add a new field to an existing database table

gistfile1.txt

Existing schema is below:

ActiveRecord::Schema.define(:version => 20120130161449) do

  create_table "movies", :force => true do |t|
    t.string   "title"
    t.string   "rating"
    t.text     "description"
    t.datetime "release_date"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

end


To add new field "director" to this schema, I created Migration by:

rails g migration AddDirectorToMovie director:string


The name "AddDirectorToMovie" means much. "Add" creates "change" method in Migration, and "ToMovie" indicates the table concerned about is "movies."


So, I got a migration file, db/migrate/20120323210944_add_director_to_movie.rb whose contents is:


class AddDirectorToMovie < ActiveRecord::Migration
  def change
    add_column :movies, :director, :string
  end
end


One last thing to do is:

rake db:migrate


Now, I have an updated schema.rb:


ActiveRecord::Schema.define(:version => 20120323210944) do

  create_table "movies", :force => true do |t|
    t.string   "title"
    t.string   "rating"
    t.text     "description"
    t.datetime "release_date"
    t.datetime "created_at"
    t.datetime "updated_at"
    t.string   "director"
  end

end


Also, I could confirm the "director" field was added on Rails console:

1.9.2p290 :012 > Movie.columns.map {|c| c.name}
 => ["id", "title", "rating", "description", "release_date", "created_at", "updated_at", "director"]

Thank you!

Wooo! Still works on Rails 5.2.3 in 2021!