final db structure

db/migrate/20170403174111_create_sale_audits.rb

@@ -0,0 +1,14 @@
+class CreateSaleAudits < ActiveRecord::Migration[5.0]
+  def change
+    create_table :sale_audits do |t|
+      t.references :sale, foreign_key: true
+      t.string :action, :null => false
+      t.datetime :action_at, :null => false
+      t.string :action_by, :null => false
+      t.string :approved_by, :null => false
+      t.datetime :approved_by, :null => false
+      t.string :remark
+      t.timestamps
+    end
+  end
+end