Re: How to access array element in pgsql after array_agg

Le 2014-06-17 à 14:22, Condor <condor(at)stz-bg(dot)com> a écrit :

> I do select array_agg(ids) from x;
> in ids I have int and result is :
>
> array_agg
> -------------
> {3843,2,3543,33}
>
> I want to access one element or first one direct in sql query like:
>
> select array_agg(ids)[1] from x;
>
> and to receive int value 2
>
> Any hints how I can do it ?

This works for me in 9.1:

psql (9.1.13)
Type "help" for help.

svanalytics=> select (array_agg(x))[1] from (values(3843),(2),(3543),(33)) t1(x) ;
array_agg
-----------
3843

Note the use of the extra parens around the array_agg call. This is probably a parser issue more than anything else.

> And also for performance did that is good I to do it in SQL or I should do it in language that I use ? The result in query will return about 2, 3 million rows.

Do you mean you will have an array of 2, 3 million elements, or 2, 3 million rows with a couple dozen elements each? I’m not sure which will be easier / faster. I routinely work with million element result sets (rows) and have no issues.

Hope that helps!
François