Only export and import comments

I have been searching around for a while but I couldn’t find how to only export and import comments from one WP installation to another.

I already exported and imported all the content but while working on my new site I got new comments to the one still online (which I don’t want to take down until the switch).

I don’t want to import the whole thing again since I will get double content, right?

So I tried to figure out how to import the comments only.
I do have access to the db direct through mysql/phpadmin but obviously I don’t know what to look for ??

Thanks in advance for any kind of help and feedback ??