Eight in a series of posts in response to Tim Ford's #EntryLevel Challenge.
My Fear Nothing post last month introduced some of the trouble that nulls can cause by generating results that are counterintuitive to what you would expect from a superficial reading of a query. This month we’ll go deeper into the rabbit hole, because the situation with nulls is rather worse than you might think.
Let’s imagine for a moment that we’re interested in answering this business question: