Re: Enhancement request: enable FIRST/LAST_value() also as a regularaggregate (not only as windowing function) - Mailing list pgsql-hackers

On 26/07/18 20:31, Tom Lane wrote:
> matshyeq <matshyeq@gmail.com> writes:
>> Can I make custom aggregate function that accepts WITHIN GROUP syntax?
> 
> It's possible, but it would have to be written in C, I think; see
> src/backend/utils/adt/orderedsetaggs.c for prototype code.  You'll
> find it a lot easier to write a plain aggregate function and control
> its input ordering with "last(foo order by foo)".

We have examples on the wiki.
https://wiki.postgresql.org/wiki/First/last_(aggregate)
-- 
Vik Fearing                                          +33 6 46 75 15 36
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