Re: Foreign Keys being able to reference same table not spelled out in documentation

Note that it is in general not necessary for the referencing column to
be NULLABLE. If you defer the constraint checking, you can insert a
cyclic structure. Of course, it's no longer a tree then.

The tutorial-ness of the documentation was already pointed out and I
don't think it needs to be said there. We just would want to not imply
this (nullable) would be necessary.

Documentation-wise I liked to MariaDB approach very much, where the two
tables were named "parent table" and "child table" and at some point
you note that it is allowed for a table to be both. But this would be a
lot more invasive.

All the Best
Mario Wenzel


Am Mittwoch, dem 05.05.2021 um 21:17 -0700 schrieb David G. Johnston:
> On Thu, Apr 29, 2021 at 10:33 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > I'm inclined to propose adding an example a little further down, as
> > per the attached draft patch.  This wouldn't help people who stop
> > reading after the section's first sentence, but we can't cover
> > everything in the first sentence.
> > 
> > 
> 
> 
> Given the tutorial nature of this section I agree with the approach.
> 
> I did a read through of the patch and I like it; though I suggest
> changing "but non-NULL" to "while non-NULL".
> 
> Thanks!
> 
> David J.
>