Re: Converting row elements into a arrays?

On 02/03/2023 20:58, Ron wrote:
> Postgresql 12.13
>
> Given the sample below, I'm looking for how to generate this output.
> It's like GROUP BY, but generating an array instead of an aggreate number.
>  f1 | f2_array
> ----+---------
> 1 | {1,2,3}
>   2 | {1,2,3,4}
>   3 | {1,2}

Something like this (off the top of my head)? -

select f1, array_agg(f2) as f2_array group by f1;

Hope that helps (and that it's right!).

Ray.

>
> The ultimate goal is to somehow use pg_index.indkey to get column names
> from pg_attribute.
>
> create table foo (f1 int, f2 int);
> insert into foo values (1, 1);
> insert into foo values (1, 2);
> insert into foo values (1, 3);
> insert into foo values (2, 1);
> insert into foo values (2, 2);
> insert into foo values (2, 3);
> insert into foo values (2, 4);
> insert into foo values (3, 1);
> insert into foo values (3, 2);
>
> select * from foo order by f1, f2;
>  f1 | f2
> ----+----
>   1 |  1
>   1 |  2
>   1 |  3
>   2 |  1
>   2 |  2
>   2 |  3
>   2 |  4
>   3 |  1
>   3 |  2
> (9 rows)
>
>
>

--
Raymond O'Donnell // Galway // Ireland
ray(at)rodonnell(dot)ie