All Fields Become Optional

As your dataset grows, exceptions creep in. There’s not enough research time to fill in all your company profiles, there’s one guy in Guam when you expected everyone to be in a U.S. state, there’s data missing from the page you’re scraping, you have to pull updates from a new source.

Every field eventually loses that beautiful NOT NULL sheen, your code gets filled up with guard clauses of one kind or another and every <div> in your template is wrapped by an if statement. And this happens to foreign keys, too, so OR IS (NOT) NULL sneaks in and left joins mutate into outer joins.