Re: Example. Foreign Keys Constraints. Wrong Columns

David G. Johnston wrote:
> On Wed, Apr 15, 2026 at 7:51 AM PG Doc comments form <noreply(at)postgresql(dot)org>
> wrote:
>
>> The following documentation comment has been logged on the website:
>>
>> Page: https://www.postgresql.org/docs/18/ddl-constraints.html
>> Description:
>>
>>
>> https://www.postgresql.org/docs/current/ddl-constraints.html#DDL-CONSTRAINTS-FK
>>
>>
> Given that users has:
>
>> PRIMARY KEY (tenant_id, user_id)
>>
>>
> This:
>
>
>> FOREIGN KEY (tenant_id, author_id) REFERENCES users ON DELETE SET NULL
>> (author_id)
>>
>>
> And this:
>
>
>> FOREIGN KEY (tenant_id, author_id) REFERENCES users (tenant_id,
>> user_id)
>> ON DELETE SET NULL (author_id)
>>
>
> Produce an identical outcome.
>
> The absence of a column list on the former causes the system to look at the
> primary key for the named table and use its column list - which is
> (tenant_id, user_id), same as the later explicit version.
>
> David J.
>

Thanks for explanation.

I think "columns mapping" (just how I call it in this example) makes
this example slightly non-intuitive, and reflects a less-common use case.
Would it help to change `author_id` to `user_id` as a more
straightforward case?

Yushu Chen