Re: Making the subquery alias optional in the FROM clause

Hi,

On Mon, Jun 27, 2022 at 12:03:20PM -0400, Isaac Morland wrote:
> On Mon, 27 Jun 2022 at 11:12, Julien Rouhaud <rjuju123@gmail.com> wrote:
>
> > More generally, I'm -0.5 on the feature.
> > I prefer to force using SQL-compliant queries, and also not take bad
> > habits.
> >
>
> As to forcing SQL-complaint queries, that ship sailed a long time ago:
> Postgres allows but does not enforce the use of SQL-compliant queries, and
> many of its important features are extensions anyway, so forcing SQL
> compliant queries is out of the question (although I could see the utility
> of a mode where it warns or errors on non-compliant queries, at least in
> principle).

Sure, but it doesn't mean that we should support even more non-compliant syntax
without any restraint.  In this case, I don't see much benefit as it's not
solving performance problem or something like that.

> As to bad habits, I'm having trouble understanding. Why do you think
> leaving the alias off a subquery is a bad habit (assuming it were allowed)?

I think It's a bad habit because as far as I can see it's not supported on
mysql or sqlserver.

> If the name is never used, why are we required to supply it?

I'm not saying that I'm thrilled having to do so, but it's also not a huge
trouble.  And since it's required I have the habit to automatically put some
random alias if I'm writing some one shot query that indeed doesn't need to use
the alias.

But similarly, I many times relied on the fact that writable CTE are executed
even if not explicitly referenced.  So by the same argument shouldn't we allow
something like this?

WITH (INSERT INTO t SELECT * pending WHERE ts < now())
SELECT now() AS last_processing_time;