rails data migration code example

Example 1: how create migration rails

rails g migration AddPartNumberToProducts

Example 2: using SQL in rails migration

def change
  execute <<-SQL
    UPDATE table1
    SET column1 = "value"
  SQL
end

Example 3: rails migration populate data

class AddSystemSettings < ActiveRecord::Migration
 	def change
      create_table :system_settings do |t|
        t.string  :name       
        t.integer  :position
      end

      # populate the table
      SystemSetting.create :name => "notice"
    end
  end