Erik Darling has opened a can of worms here:
WITH ALL THE TROUBLE NULLS CAUSE…
You’d think people would be more inclined to avoid them. Slap a NOT NULL constraint and a default value on your column and call it a day. I’m perfectly fine with bizarro world canary values. If it’s an integer column, some really high (low?) negative number. If it’s date-based, why not have it be the lowest value your choice accomodates?
Check out the comments, definitely. I don’t think it’s as clear-cut as Erik argues; the idea of NULL has been and will remain controversial because it’s a useful concept but one which requires explicit consideration.