sql - How to get an array in postgres where the array size is greater than 1 -

i have table looks this:

val | fkey | num ------------------ 1   |  1   | 1 1   |  2   | 1   1   |  3   | 1   2   |  3   | 1

what return set of rows in values grouped 'val', array of fkeys, array of fkeys greater 1. so, in above example, return like:

1 | [1,2,3]

i have following query aggregates arrays:

select val, array_agg(fkey) mytable group val;

but returns like:

1 | [1,2,3] 2 | [3]

what best way of doing this? guess 1 possibility use existing query subquery, , sum / count on that, seems inefficient. feedback help!

use having clause filter groups having more fkey

select val, array_agg(fkey) mytable group val having count(fkey) > 1

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