定语从句中的关系词为关系副词时,从句有没有介词?

一般来说，关系副词和介词不会连用。
但是，对于介词 from，可能出现一些特殊情况。如：
Beijing is the place where he comes from.
（正如可以说：Where does he come from? 或 Where is he from?）
The school library is the place where he got the book from.
（这一句中from也可以不用。）
His head soon appeared out of the second-storey windows, from where he could see nothing but trees. (这一句where 也可改用which.)
（比较：His head soon appeared out of the second-storey windows. From there he could see nothing but trees.）

介词不可以和副词连用
但是句子中可以有介词

比如;this is the place where i used to live.

live 后面不可以有介词，但句子中可有介词