How is category_count updated?

Hello, because of the batch number of posts I have to post everyday, I prepare my database on my computer and then I update my database thru phpmyadmin.. This is how I used to do in my previous blog CMS.. Now that I have switched to WP.. I have gone thru many things but could not find this one:

I can update or insert my posts into desired categories thru phpmyadmin (because I have to post hundreds or thousands of post everyday as it is a yellow pages site)

But I did not understand how to update category_count column in wp_categories table.. How does WP updates this value everytime a new post is inserted into a category normally thru wp-admin interface? what SQL command does it use?

thanks..