>>>All in all, they're really the same thing.
>>
>>No, your code is not the same as Dmitry's and it doesn't test all conditions.
>
>How so?

You're right, actually, I just realised that (wanted to update my reply, but it was too late) and made a quick test. It is indeed the same and it's better, though perhaps still not obvious and ISNULL tests would be more transparent (or some comments may help).