Query: rds_db_instances_for_rds_db_cluster

with rds_db_cluster as (
  select
    arn,
    db_cluster_identifier,
    region,
    account_id
  from
    aws_rds_db_cluster
  where
    account_id = split_part($1, ':', 5)
    and region = split_part($1, ':', 4)
    and arn = $1
  order by
    arn,
    db_cluster_identifier,
    region,
    account_id
), rds_db_instance as (
  select
    arn,
    db_cluster_identifier,
    region,
    account_id
  from
    aws_rds_db_instance
  order by
    arn,
    db_cluster_identifier,
    region,
    account_id
)
select
  i.arn as instance_arn
from
  rds_db_instance as i
  join rds_db_cluster as c on i.db_cluster_identifier = c.db_cluster_identifier