Рост стоимости клика по кампаниям месяц к месяцу

SQL, по которому посчитано

WITH bounds AS (
  SELECT
    date_trunc('month', max(date))::DATE AS current_month,
    (date_trunc('month', max(date)) - INTERVAL '1 month')::DATE AS previous_month
  FROM ads
),
monthly AS (
  SELECT
    source,
    campaign,
    date_trunc('month', date)::DATE AS month_start,
    sum(clicks) AS clicks,
    sum(cost) AS cost
  FROM ads
  WHERE date >= (SELECT previous_month FROM bounds)
    AND date < (SELECT current_month FROM bounds) + INTERVAL '1 month'
  GROUP BY source, campaign, month_start
),
pivoted AS (
  SELECT
    source,
    campaign,
    max(CASE WHEN month_start = (SELECT current_month FROM bounds) THEN clicks END) AS clicks_current,
    max(CASE WHEN month_start = (SELECT previous_month FROM bounds) THEN clicks END) AS clicks_previous,
    max(CASE WHEN month_start = (SELECT current_month FROM bounds) THEN cost END) AS cost_current,
    max(CASE WHEN month_start = (SELECT previous_month FROM bounds) THEN cost END) AS cost_previous
  FROM monthly
  GROUP BY source, campaign
)
SELECT
  source || ' / ' || campaign AS campaign_label,
  source,
  campaign,
  clicks_previous,
  clicks_current,
  round(cost_previous / nullif(clicks_previous, 0), 2) AS cpc_previous_rub,
  round(cost_current / nullif(clicks_current, 0), 2) AS cpc_current_rub,
  round(
    (cost_current / nullif(clicks_current, 0)) /
    nullif(cost_previous / nullif(clicks_previous, 0), 0) - 1,
    4
  ) AS cpc_growth
FROM pivoted
WHERE clicks_previous > 0
  AND clicks_current > 0
ORDER BY cpc_growth DESC NULLS LAST
LIMIT 30