A lot of the time, we're checking if UPDATE is successful by doing if ($stmt->rowCount() > 0). However, if you update a row with an identical value, this returns 0. This is fine for the most part, but in a few cases (like on user registration, when we set a user's primary group to its current value) we get an error when we shouldn't.
So, we need a better way to determine if these operations are 'successful' (and also try to decide what success actually means for these operations).