You can’t prove a negative, but what about querying a database for a negative? While the majority of the time you are writing queries to find data, there are some cases when you want the opposite: writing a query that looks for the absence of data.
Susan was hired as a database engineer. Her primary projects, keep slipping. But she is one of HR’s favorite people because she is always available to interview, even at short notice, and gives brilliant, in-depth feedback on candidates.