Re: nicer examples for aggregate calls

On Sat, Oct 23, 2021 at 01:51:48PM +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
> 
> Page: https://www.postgresql.org/docs/14/tutorial-agg.html
> Description:
> 
> currently, all of the examples are very simple, like
> 
> SELECT city, max(temp_lo)
>     FROM weather
>     WHERE city LIKE 'S%'            -- (1)
>     GROUP BY city
>     HAVING max(temp_lo) < 40;
> 
> this example would be more complex and would allow users to search for
> clause "filter":
> 
> Finally, if we only care about cities whose names begin with “S” and we want
> to calculate the number of observations in each city with temp_lo over 30,
> we might do:
> 
> SELECT city, max(temp_lo), count(*) filter (temp_lo>30), 
>     FROM weather
>     WHERE city LIKE 'S%'            -- (1)
>     GROUP BY city
>     HAVING max(temp_lo) < 40;

Good idea.  We didn't support FILTER at the time this query was added.
Here is a patch which adds it.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Indecision is a decision.  Inaction is an action.  Mark Batterson