Yeah thats it, I've never seen contraints used that much in the real world. Unique keys but thats about it. Clever database-level contraints usually come back a

Yeah thats it, I've never seen contraints used that much in the real world. Unique keys but thats about it. Clever database-level contraints usually come back and bite you in the arse when you're trying to do some large scale change or upgrade or fix. And if you're building an app you usually want the validation of input to be done as close to the user as possible (like in the UI), not relying on a round trip to the database and handling an exception. And some might say 'well have validation in both places' but then you've got a load of complex stuff to keep in sync which will be a pain in the arse if it gets out of sync (if your db rules differ slightly from your ui rules)