Where is the code that sends order data to the database?

I am looking for the code (SQL query) which sends the order data to the database (items, comments, delivery info, etc.). Where would I find this?

Thanks,
BParker

There are many parts of the code that trigger that, depending on what you're trying to do.
Your question implies that maybe you're planning to intercept the normal code and hack in some changes to what is stored, perhaps adding extra info to be stored. And while your first instinct appears to be that you intend to just hack the core code file to do it in the order.php class file, chances are you want to make your changes easier to manage through an upgrade, and thus you should be using notifier hooks to make your changes in custom observer class files that you add to the site.

So ... what exactly are you intending to do? What business problem are you really trying to solve?