I don't believe the relational model is as rigid as you described. The fact is that there are many different ways to model the same business concept in the real...

Interesting approach.

But all three examples cause a clustered index scan. I wonder if the author thought about that. I would not use such queries on a large table.

I agree with Antares686. MS needs to address the limitations with CAST. Having said that, I do use CAST a lot.