Query: ibm_compute_instance_disk_storage_by_creation_month

  with disks as (
    select
      title,
      created_at,
size,
      to_char(created_at,
        'YYYY-MM') as creation_month
    from
      ibm_is_instance_disk
  ),
  months as (
    select
      to_char(d,
        'YYYY-MM') as month
    from
      generate_series(date_trunc('month',
          (
            select
              min(created_at)
              from disks)),
          date_trunc('month',
            current_date),
          interval '1 month') as d
  ),
  disks_by_month as (
    select
      creation_month,
      sum(size)
    from
      disks
    group by
      creation_month
  )
  select
    months.month,
    disks_by_month.sum as "GB"
  from
    months
    left join disks_by_month on months.month = disks_by_month.creation_month
  order by
    months.month;