Query: rds_db_subnet_groups_for_rds_db_instance

select
  g.arn as db_subnet_group_arn
from
  aws_rds_db_instance as i,
  aws_rds_db_subnet_group g
where
  i.db_subnet_group_name = g.name
  and i.region = g.region
  and i.account_id = g.account_id
  and i.arn = $1;