ARRAY() with SELECT AS STRUCT

query.sql

SELECT c.borough,c.year,
    ARRAY(
      select as struct c2.month,sum(value) crime_tally
      from `bigquery-public-data.london_crime.crime_by_lsoa` as c2
      where c.borough = c2.borough
        and c.year = c2.year
      group by c2.month
    ) as monthly_summary
FROM (
  select distinct borough,year
  from `bigquery-public-data.london_crime.crime_by_lsoa` c
) c