> The background here is that the SQL standard was ambiguous about which of the two ways an implementation should behave. So in the upcoming SQL:202x, this was addressed by making the behavior implementation-defined and adding this NULLS [NOT] DISTINCT option to pick the other behavior.
Oracle behaves the same as Postgres with regards to NULL values in unique indexes.
> I guess this does go against the spec?
The first comment (by the blog author) https://news.ycombinator.com/item?id=32054151 explained this:
> The background here is that the SQL standard was ambiguous about which of the two ways an implementation should behave. So in the upcoming SQL:202x, this was addressed by making the behavior implementation-defined and adding this NULLS [NOT] DISTINCT option to pick the other behavior.