* equivalence relations, for example if {@code set1} is a {@link HashSet} and {@code set2} is a
   * {@link TreeSet} or the {@link Map#keySet} of an {@code IdentityHashMap}.
   */
  public static <E extends @Nullable Object> SetView<E> difference(Set<E> set1, Set<?> set2) {
    checkNotNull(set1, "set1");
    checkNotNull(set2, "set2");

    return new SetView<E>() {

      Set<? extends E> set1, Set<? extends E> set2) {
    checkNotNull(set1, "set1");
    checkNotNull(set2, "set2");

    return new SetView<E>() {
      @Override
      public int size() {
        int size = set1.size();
        for (E e : set2) {
          if (!set1.contains(e)) {
            size++;
          }
        }
        return size;
      }

	DB.Save(GetUser("joins-args-db", Config{Pets: 2}))

	if err := DB.Migrator().CreateView("invalid_users_pets",
		gorm.ViewOption{Query: nil}); err != gorm.ErrSubQueryRequired {
		t.Fatalf("no view should be created, got %v", err)
	}

	query := DB.Model(&User{}).
		Select("users.id as users_id, users.name as users_name, pets.id as pets_id, pets.name as pets_name").

				"application/x-mscardfile",
				"application/x-msclip",
				"application/x-msdownload",
				"application/x-ms-installer",
				"application/x-msdownload;format=pe",
				"application/x-msdownload;format=pe32",
				"application/x-msdownload;format=pe64",
				"application/x-msdownload;format=pe-itanium",
				"application/x-msdownload;format=pe-armLE",
				"application/x-msdownload;format=pe-arm7",

	}
}

func TestQueryWithAssociation(t *testing.T) {
	user := *GetUser("query_with_association", Config{Account: true, Pets: 2, Toys: 1, Company: true, Manager: true, Team: 2, Languages: 1, Friends: 3})

	if err := DB.Create(&user).Error; err != nil {
		t.Fatalf("errors happened when create user: %v", err)
	}