| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | Vik Fearing <vik(at)postgresfriends(dot)org> |
| Cc: | Zsolt Parragi <zsolt(dot)parragi(at)percona(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Jacob Champion <jacob(dot)champion(at)enterprisedb(dot)com>, Isaac Morland <isaac(dot)morland(at)gmail(dot)com> |
| Subject: | Re: Logical Implication |
| Date: | 2026-11-06 20:05:23 |
| Message-ID: | au4zAwo3wQ-KfOh-@nathan |
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| Lists: | pgsql-hackers |
On Tue, Oct 06, 2026 at 01:19:31PM -0500, Nathan Bossart wrote:
> On Sat, Oct 03, 2026 at 06:18:43PM +0200, Vik Fearing wrote:
>> <acronym>SQL</acronym> uses a three-valued logic system with true,
>> - false, and <literal>null</literal>, which represents <quote>unknown</quote>.
>> - Observe the following truth tables:
>> + false, and unknown; the null value of a <type>boolean</type> and the truth
>> + value unknown are one and the same. In the truth tables below the left
>> + operand of a binary operator selects the row, and the right operand the
>> + column:
>
> I find the reorganization to be an improvement, and I intend to commit this
> one sooner than later. The only thing I'd change is the switch from NULL
> to "unknown" in the tables. Users deal with NULL at the command level, and
> the rest of the docs use NULL, so I think the existing text has the right
> idea by noting once that NULL represents "unknown" and then using NULL
> throughout.
Concretely, like the attached.
--
nathan
| Attachment | Content-Type | Size |
|---|---|---|
| v4-0001-doc-Rearrange-the-logical-operator-truth-tables.patch | text/plain | 4.0 KB |
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