BigQuery GROUP_CONCAT and ORDER BY

Question

I am currently using BigQuery and GROUP_CONCAT which works perfectly fine. However, when I try to add a ORDER BY clause to the GROUP_CONCAT statement like I would do in SQL,

Answer 1

Here is a version in Standard SQL mode in BigQuery with ARRAY_AGG as aggregate function:

select key,
array_agg(struct(grouped_value) order by array_length(grouped_value) desc limit 1)[offset(0)].*
from (
select 
  key, 
  array_agg(value) over 
    (partition by key
     order by value asc
     rows between unbounded preceding and unbounded following) 
  grouped_value 
from (
select key, value from unnest([
    struct(1 as key, "b" as value)
  , struct(1, "c")
  , struct(1, "a")
  , struct(2, "y")
  , struct(2, "x")
]))) group by key