Re: Set Returning Functions and array_agg() - Mailing list pgsql-general

On 2013-04-24, Stephen Scheck <singularsyntax@gmail.com> wrote:
> --f46d043c810aa794a404db21f464
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>
> Possibly due to my lack of thorough SQL understanding. Perhaps there's a
> better way of doing what I'm ultimately trying to accomplish, but still the
> question remains - why does this work:
>
> pg_dev=# select unnest(array[1,2,3]);
>  unnest
> --------
>       1
>       2
>       3
> (3 rows)
>
> But not this:
>
> pg_dev=# select array_agg(unnest(array[1,2,3]));
> ERROR:  set-valued function called in context that cannot accept a set

the parser doesn't understand it for the reason given

same as it doesn't understand this.

 select avg(generate_series(1,3));

but it does understand this:

 select avg(a) from  generate_series(1,3) as s(a);

and this:

 select array_agg(i) from unnest(array[1,2,3])) as u(i);




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