Theo dõi MAU (II)

WITH mau AS (
  SELECT
    DATE_TRUNC('month', order_date) :: DATE AS delivr_month,
    COUNT(DISTINCT user_id) AS mau
  FROM orders
  GROUP BY delivr_month),

  mau_with_lag AS (
  SELECT
    delivr_month,
    mau,
    -- Fetch the previous month's MAU
    COALESCE(
      ___,
    0) AS last_mau
  FROM mau)

SELECT
  -- Calculate each month's delta of MAUs
  ___,
  ___ AS mau_delta
FROM mau_with_lag
-- Order by month in ascending order
ORDER BY ___;