Add All Posts to Category

I have 37 articles on my blog. All English. There’s no English category. Later, when I switch to multi-lingual and I need to post in other languages, I’ll need to tag all my current posts into the English tag. It might take a lot of effort to do manually.

Can I play with the database to achieve this with an SQL statement or two? I noticed, in the post2cat table, it contains information on pages, posts, and other things–attachments, I think?