005_create_articles_tags.rb

# in db/migrateclass CreateArticlesTags < ActiveRecord::Migration  def self.up    create_table :articles_tags do |t|      t.integer :article_id      t.integer :tag_id    end      end  def self.down    drop_table :articles_tags  endend# in app/models/article.rbclass Article < ActiveRecord::Base  has_and_belongs_to_many :tagsend# in app/models/tag.rbclass Tag < ActiveRecord::Base  has_and_belongs_to_many :articlesend