On Thu, Jan 19, 2023 at 3:41 PM Adrian Klaver <adrian.kla...@aklaver.com> wrote:
> From here: > > https://www.postgresql.org/about/featurematrix/detail/392/ > > UNIQUE NULLS NOT DISTINCT > > By default, NULL values are not treated as distinct entries. Specifying > NULLS NOT DISTINCT on unique indexes / constraints will cause NULL > values to be treated distinctly. > > > From here: > > https://www.postgresql.org/docs/current/sql-createindex.html > > NULLS DISTINCT > NULLS NOT DISTINCT > > Specifies whether for a unique index, null values should be > considered distinct (not equal). The default is that they are distinct, > so that a unique index could contain multiple null values in a column. > > and here: > > https://www.postgresql.org/docs/current/sql-createtable.html > > For the purpose of a unique constraint, null values are not considered > equal, unless NULLS NOT DISTINCT is specified. > > I think saying that NULLs are distinct by default is the better way to present this. The documentation disagrees on the verbiage but both state the same truth; the feature matrix page needs to be fixed. David J.
