Re: Document NULL

On Thu, 2 May 2024 at 03:12, David G. Johnston
<david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
> Attached is a very rough draft attempting this, based on my own thoughts and those expressed by Tom in [1], which largely align with mine.

Thanks for picking this up. I agree that we should have something to
improve this.

It would be good to see some subtitles in this e.g "Three-valued
boolean logic" and document about NULL being unknown, therefore false.
Giving a few examples would be good to, which I think is useful as it
at least demonstrates a simple way of testing these things using a
simple FROMless SELECT, e.g. "SELECT NULL = NULL;". You could link to
this section from where we document WHERE clauses.

Maybe another subtitle would be "GROUP BY / DISTINCT clauses with NULL
values", and then explain that including some other examples using
"SELECT 1 IS NOT DISTINCT FROM NULL;" to allow the reader to
experiment and learn by running queries.

You likely skipped them due to draft status, but if not, references
back to other sections likely could do with links back to that
section, e.g "amount of precipitation Hayward" is not on that page.
Without that you're assuming the reader is reading the documents
linearly.

Another section might briefly explain about disallowing NULLs in
columns with NOT NULL constraints, then link to wherever we properly
document those.

typo:

+ <title>Handling Unkowns (NULL)</title>

Maybe inject "Values" after Unknown.

Let's bash it into shape a bit more before going any further on actual wording.

David