We don't use relative clauses to define objects but reduced adjective clauses, in any possible case (i.e. when the relative pronoun can be the subjective in the relative clause) . You can see the translation for your sentences for instance.
Well, we also use clause in this case but it is just colloquial language.
E.g. : Anh chàng, cái người mà hôm qua tặng hoa cho cậu ý, ở ngay cạnh nhà mình.
The boy who gave you flowers yesterday lives next to my door.
In other cases, where reduced adjective clauses cannot be used, especially when the clause is used to define the time and place, we use defining relative clauses. And in Vietnamese grammar, it is "câu phức thành phần định ngữ".
For example:
Cái máy (mà) tôi đang dùng đã cũ quá rồi.
The machine which I am using is too old
Ngày (mà) tôi gặp cô ấy là một ngày tuyết rơi.
The day when I met her was a snowy day.
Nơi (mà) tôi sinh ra là một căn gác nhỏ giữa phố cổ Hà Nội.
The place where I was born is a small attic in the Old Quarter of Hanoi.
As you can see, the relative pronoun is "mà" but it is often odded out.