Consider the English:
The chair which he sat on
The chair on which he sat
Of course, the latter is grammatically correct English, yet the former has a much wider use in spoken and, in some cases, written English that it has become the most accepted.
However, in French, the only way I know of doing it is by writing an equivalent of the latter:
La chaise sur laquelle je m'assieds
What I was wondering was if French had adopted a version of the former, or simply use it like the example above
I am guessing that the following is not correct but is my only idea at what a translation if the former could be
La chaise laquelle je m'assieds sur
Merci!