Why does NULL = NULL evaluate to false in SQL server

Question

In SQL server if you have nullParam=NULL in a where clause, it always evaluates to false. This is counterintuitive and has caused me many errors. I do understa

Answer 1

To quote the Christmas analogy again:

In SQL, NULL basically means "closed box" (unknown). So, the result of comparing two closed boxes will also be unknown (null).

I understand, for a developer, this is counter-intuitive, because in programming languages, often NULL rather means "empty box" (known). And comparing two empty boxes will naturally yield true / equal.

This is why JavaScript for example distinguishes between null and undefined.