root/db/migrate/007_create_gallery_medias.rb

class CreateGalleryMedias < ActiveRecord::Migration
  def self.up
    create_table :gallery_medias do |t|
              t.string :sTitle
              t.text :tDescription
              t.string :medianame
              t.references :gallery
      t.timestamps
    end
  end

  def self.down
    drop_table :gallery_medias
  end
end