It’s no secret that you are not supposed to touch SharePoint databases but there certainly are some scenarios which would tempt you to at least read from them; mostly for performance reasons. For example, if you want to do some kind of reporting with data pulled from lists spread over 15K sites, it’s not a terrible sin to read from content database directly. So, if in any shape or form your code is interacting with database directly you have some work to do to make it work in 2010. It shouldn’t be a surprise that SQL boys in Redmond campus have tweaked the SharePoint 2010 databases.
I did a SQL compare of 2007 and 2010 content databases and here’s my findings:
Identical Tables (9):
New Tables (16):
Dropped Tables (4):
Rest of the tables, 78 of them, have their schema modified. So, as you can see, pretty much every table has been re-done. Start making your changes to get ready for 2010. Good times.