Table: aws_cost_forecast_monthly

select
  period_start,
  period_end,
  mean_value :: numeric :: money
from
  aws_cost_forecast_monthly
order by
  period_start;

with cost_data as (
  select
    period_start,
    mean_value as this_month,
    lag(mean_value, -1) over(
      order by
        period_start desc
    ) as previous_month
  from
    aws_cost_forecast_monthly
)
select
  period_start,
  this_month :: numeric :: money,
  previous_month :: numeric :: money,
  case
    when previous_month = 0
    and this_month = 0 then 0
    when previous_month = 0 then 999
    else round(
      (100 * ((this_month - previous_month) / previous_month)) :: numeric,
      2
    )
  end as percent_change
from
  cost_data
order by
  period_start;