I can understand that, and in fact I wondered a bit about posting something with relevance quite as tangential or indirect as this, and more about the history of programming than about current practise. But in the end I thought that on balance it might be worth reminding people that defensive programming has been recognised as a need in computing since the very start of the programming stored program computers. Besides, I wanted an easy ride on my first QOTD so that it wouldn't have too many people picking holes in the answer or in the explanation and this was one I thought I couldn't get wrong (I was wrong about that - there's a glaring typing error in the explanation, as has already been pointed out). I expected most people would guess rather than resort to google, but I can't see why anyone would regard use of google as cheating on a question like this; and I was very surprised to see that TPTB had decided to make it worth 6 points, because it is not at all an SQLServer question - although some of the questions tagged humour have been even less relevant yet still higher scoring.

But don't worry, my next QOTD (assuming it gets accepted - it's been pending a while) is T-SQL straight and simple, and I hope that will be more to your taste.