alt Hacker NewsHow is “not available yet” different from "Don't know"? How is incomputable different from “will never be available”?
> SQL shouldn’t even have null
But it needs to, because it needs to represent half of a result record not existing, i.e. on a LEFT JOIN.
"Not available yet", at least to me, carries the implication that it will, not just might, become available at some point. Probably soon enough that it's worth asking the question again later. Whereas "don't know" suggests that it's not worth asking the question again, because you're probably just going to get "don't know" as the answer. (At least, if "don't know" and "not available yet" are both presented as options).