我有两个模型：
class User
default_scope -> { where(deleted_at: nil) }
end
class Order
belongs_to :user
end
我想获得已删除或未删除用户的订单：
Order.joins(:user).merge(User.unscoped)
Order.joins(:user).merge(User.unscope(where: :deleted_at))
# SELECT "orders".* FROM "orders"
# INNER JOIN "users" ON "users"."id" = "orders"."user_id" AND "users"."deleted_at" IS NULL
# ORDER BY "orders"."id" DESC LIMIT 1
Order.eager_load(:user).merge(User.unscoped)
Order.eager_load(:user).merge(User.unscope(where: :deleted_at))
# SELECT "orders"."id" AS t0_r0, "orders"."user_id" AS t0_r1,
# "users"."id" AS t1_r0, "users"."deleted_at" AS t1_r1 FROM "orders"
# LEFT OUTER JOIN "users" ON "users"."id" = "orders"."user_id" AND "users"."deleted_at" IS NULL
# ORDER BY "orders"."id" …