DECLARE today DATE DEFAULT DATE_SUB(CURRENT_DATE(), INTERVAL 1 DAY);
DECLARE baseline_start DATE DEFAULT DATE_SUB(today, INTERVAL 14 DAY);

WITH daily AS (
  SELECT
    DATE(usage_start_time) AS usage_date,
    service.description    AS service,
    sku.description        AS sku,
    SUM(cost)              AS daily_cost
  FROM `@project_id.@dataset.@table`
  WHERE DATE(_PARTITIONTIME) BETWEEN baseline_start AND today
    AND project.id        = @project_id
    AND currency          = 'USD'
    AND cost IS NOT NULL
  GROUP BY usage_date, service, sku
),
...