Thread

Re: Document NULL

Thom Brown <thom@linux.com> — 2024-05-11T17:51:37Z

On Sat, May 11, 2024, 16:34 David G. Johnston <david.g.johnston@gmail.com>
wrote:

> On Fri, May 3, 2024 at 9:00 AM David G. Johnston <
> david.g.johnston@gmail.com> wrote:
>
>> On Fri, May 3, 2024 at 8:44 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>
>>> Having said that, I reiterate my proposal that we make it a new
>>>
>> <sect1> under DDL, before 5.2 Default Values which is the first
>>> place in ddl.sgml that assumes you have heard of nulls.
>>
>>
>> I will go with this and remove the "Data Basics" section I wrote, leaving
>> it to be just a discussion about null values.  The tutorial is the only
>> section that really needs unique wording to fit in.  No matter where we
>> decide to place it otherwise the core content will be the same, with maybe
>> a different section preface to tie it in.
>>
>>
> v3 Attached.
>
> Probably at the 90% complete mark.  Minimal index entries, not as thorough
> a look-about of the existing documentation as I'd like.  Probably some
> wording and style choices to tweak.  Figured better to get feedback now
> before I go into polish mode.  In particular, tweaking and re-running the
> examples.
>
> Yes, I am aware of my improper indentation for programlisting and screen.
> I wanted to be able to use the code folding features of my editor.  Those
> can be readily un-indented in the final version.
>
> The changes to func.sgml is basically one change repeated something like
> 20 times with tweaks for true/false.  Plus moving the discussion regarding
> the SQL specification into the new null handling section.
>
> It took me doing this to really understand the difference between row
> constructors and composite typed values, especially since array
> constructors produce array typed values and the constructor is just an
> unimportant implementation option while row constructors introduce
> meaningfully different behaviors when used.
>
> My plan is to have a v4 out next week, without or without a review of this
> draft, but then the subsequent few weeks will probably be a bit quiet.
>

+   The cardinal rule, a given null value is never
+   <link linkend="functions-comparison-op-table">equal or unequal</link>
+   to any other non-null.

Again, doesn't this imply it tends to be equal to another null by its
omission?

Thom

>