rails g migration add_yyyymm_to_messages yyyymm:integer

Author: amatsuda

db/migrate/20251220051221_add_yyyymm_to_messages.rb

@@ -0,0 +1,5 @@
+class AddYyyymmToMessages < ActiveRecord::Migration[8.1]
+  def change
+    add_column :messages, :yyyymm, :integer
+  end
+end