Re: https://gist.github.com/hamakn/6a87a3463794754ac142741d5535f067#dbの設計について

schema.rb

create_table "users" do |t|
  t.string  "name", null: false
end

create_table "itames" do |t|
  t.string  "name", null: false
  t.t.integer  "category_id", limit: 4, null: false
  t.t.integer  "user_id", limit: 4, null: false
end

create_table "categories" do |t|
  t.string  "name", null: false
end

create_table "available_items" do |t|
  t.integer  "item_id", limit: 4, null: false
  t.t.integer  "category_id", limit: 4, null: false
  t.t.integer  "user_id", limit: 4, null: false
end

add_index "available_items", ["category_id", "user_id"], unique: true