On Tue, Nov 8, 2022 at 05:22:24PM -0500, Tom Lane wrote:
> PG Doc comments form <noreply@postgresql.org> writes:
> > Hello: I am working through the tutorial and the Doc page says the row count
> > is 5 but my results show 0 records. Of course, I may be doing something
> > wrong, too:
>
> > jwjwj=# SELECT city, max(temp_lo), count(*) FILTER (WHERE temp_lo < 30)
> > FROM weather
> > GROUP BY city
> > HAVING max(temp_lo) < 40;
> > city | max | count
> > ---------+-----+-------
> > Hayward | 37 | 0
> > (1 row)
>
> No, you're right, given the sample data shown earlier then count = 0
> is what you would get. Somebody injected this FILTER example without
> a lot of thought, it would appear, as not only does the output not
> match but it's completely disjointed from the flow of explanation
> (IMO anyway). This example originally introduced only HAVING, and
> trying to make it do double duty just confuses things. A fully
> separate example of FILTER would have served better.
>
> I'll go do something about that --- thanks for the report!
Sorry, that was me, and I thought I checked it, but obviously
incorrectly, thanks.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EDB https://enterprisedb.com
Indecision is a decision. Inaction is an action. Mark Batterson