Two decades ago, the topic of "NULL" came up in conversation with a scholarly colleague. As I remember it, he said that C.J.Date, in an essay critical of commercial implementations of SQL, had listed over two hundred meanings for NULL. To my regret, I did not persist the details; but finding that list has since been on my Bucket List. Has anyone else heard this legend? Was it perhaps not Date, but another critic of commercial implementations of SQL?