Re: Set Returning Functions and array_agg()

On 2013-04-24, Stephen Scheck <singularsyntax(at)gmail(dot)com> wrote:
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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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