Re: Converting row elements into a arrays?

On 3/2/23 15:45, Rob Sargent wrote:

On 3/2/23 13:58, 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}

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);

[snip]

In which environment are you accessing that array?  psql only?

Correct.

For multiple columns it's a litte messier ( if you have different data types in your columns)

create table foo (f1 int, f2 int, f3 text);
insert into foo values (1, 1,'asdf');
insert into foo values (1, 2, 'qerr');

select f1, array_agg(array[f2::text,f3]) from foo group by f1;
 f1 |      array_agg      
----+---------------------
  1 | {{1,asdf},{2,qerr}}
(1 row)