final db structure

db/migrate/20170403162221_create_sale_discounts.rb

@@ -0,0 +1,13 @@
+class CreateSaleDiscounts < ActiveRecord::Migration[5.0]
+  def change
+    create_table :sale_discounts do |t|
+      t.references :sale, foreign_key: true
+      t.string :discount_type, :null => false
+      t.decimal :discount_value, :precision => 10, :scale => 2, :null => false, :default => 0.00
+      t.decimal :discount_amount, :precision => 10, :scale => 2, :null => false, :default => 0.00
+      t.string :discount_code
+
+      t.timestamps
+    end
+  end
+end