Add fields to an existing table¶
shell$ script/generate migration AddAddressToPoliticians
codetitle. db/migrations/002_add_address_to_politicians.rb
class AddAddressToPoliticians < ActiveRecord::Migration
def self.up
add_column :politicians, :address, :string
end
def self.down
remove_column :politicians, :address
end
end
shell$ rake db:migrate
the available column types are: boolean, integer, float, string, text, datetime, blob
Changing the default values¶
change_column(table_name, column_name, type, options)When you need to execute raw SQL¶
Sometimes you need to execute raw SQL in your migration. In general, this should be avoided when possible, because may lock your application to a specific database.
class AlterWatchInUserParticipations < ActiveRecord::Migration
def self.up
execute "ALTER TABLE `user_participations` ALTER COLUMN `watch` SET DEFAULT FALSE"
end
def self.down
execute "ALTER TABLE `user_participations` ALTER COLUMN `watch` DROP DEFAULT"
end
end
