Is There a Way to Combine Validation Rules in a Data Base?

In s p dot nat, when you have a model for the deto, you can put annotations on it. And i think what you're saying that you can do is that you can keep those sort of validation rules inside the domain objects that you create. You still have your validation rules in one place. What's approach to when you have code based that has exceptions and it passes back knolls, the calls to the data base are sort of mixed in with the objects? How do you start that process of bringing in more functional concepts, or just bringing in more concepts that are easier to follow understand?