[taneq]

Everyone hates null but (in database land, and arguably in other programming) it just means “no data.”

(As an aside, I found the characterisation of null as being a “billion dollar mistake” to be unfair. Those who don’t acknowledge null are doomed to reimplement it, probably poorly, or to have the unknowns in their logic remain unknown unknowns.)

[mcherm]

The "mistake" was not in providing a way to represent "no data", it was in providing no way to represent "this definitely HAS" data.

Languages that correct the problem have two separate types (eg: Foo & Option<Foo>) meaning "definitely a Foo" and "a Foo but it might have no data". Java just has Foo, meaning "a Foo but it might have no data" but no way to represent "definitely a Foo".