SELECT
  invoice.month,
  SUM(cost)
    + SUM(IFNULL((SELECT SUM(c.amount)
                  FROM UNNEST(credits) c), 0))
    AS total,
  (SUM(CAST(cost AS NUMERIC))
    + SUM(IFNULL((SELECT SUM(CAST(c.amount AS NUMERIC))
                  FROM UNNEST(credits) AS c), 0)))
    AS total_exact
FROM `project.dataset.gcp_billing_export_v1_XXXXXX_XXXXXX_XXXXXX`
GROUP BY 1
ORDER BY 1 ASC
;

SELECT
    invoice.month AS invoice_month,
    SUM(cost) as commitment_fees
FROM `project.dataset.gcp_billing_export_v1_XXXXXX_XXXXXX_XXXXXX`
WHERE LOWER(sku.description) LIKE "commitment%"
GROUP BY 1

SELECT
    invoice.month AS invoice_month,
    SUM(credits.amount) as CUD_credits
FROM `project.dataset.gcp_billing_export_v1_XXXXXX_XXXXXX_XXXXXX`
LEFT JOIN UNNEST(credits) AS credits
WHERE credits.type = "COMMITTED_USAGE_DISCOUNT"
GROUP BY 1