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doc: use FILTER in aggregate example 

Reported-by: michal.palenik@freemap.sk

Discussion: https://postgr.es/m/163499710897.684.7420075366995883688@wrigleys.postgresql.org

Backpatch-through: 10
This commit is contained in:
Bruce Momjian 2022-08-31 22:19:06 -04:00
parent 4e3eb6dd1a
commit d55fdfb554
1 changed files with 7 additions and 6 deletions
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13
doc/src/sgml/query.sgml
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@ -728,19 +728,20 @@ SELECT city, max(temp_lo)
which gives us one output row per city. Each aggregate result is which gives us one output row per city. Each aggregate result is
computed over the table rows matching that city. computed over the table rows matching that city.
We can filter these grouped We can filter these grouped
rows using <literal>HAVING</literal>: rows using <literal>HAVING</literal> and the output count using
<literal>FILTER</literal>:
<programlisting> <programlisting>
SELECT city, max(temp_lo) SELECT city, max(temp_lo), count(*) FILTER (WHERE temp_lo &lt; 30)
FROM weather FROM weather
GROUP BY city GROUP BY city
HAVING max(temp_lo) &lt; 40; HAVING max(temp_lo) &lt; 40;
</programlisting> </programlisting>
<screen> <screen>
city | max city | max | count
---------+----- ---------+-----+-------
Hayward | 37 Hayward | 37 | 5
(1 row) (1 row)
</screen> </screen>
@ -750,7 +751,7 @@ SELECT city, max(temp_lo)
names begin with <quote><literal>S</literal></quote>, we might do: names begin with <quote><literal>S</literal></quote>, we might do:
<programlisting> <programlisting>
SELECT city, max(temp_lo) SELECT city, max(temp_lo), count(*) FILTER (WHERE temp_lo &lt; 30)
FROM weather FROM weather
WHERE city LIKE 'S%' -- <co id="co.tutorial-agg-like"/> WHERE city LIKE 'S%' -- <co id="co.tutorial-agg-like"/>
GROUP BY city GROUP BY city