Коэффициент вариации продаж
SQL, по которому посчитано
WITH monthly AS (
SELECT product, date_trunc('month', date) AS month, sum(units) AS units
FROM sales
WHERE date > (SELECT max(date) FROM sales) - INTERVAL 12 MONTH
GROUP BY ALL
)
SELECT product, round(stddev_pop(units) / avg(units), 4) AS variation
FROM monthly
GROUP BY product
ORDER BY variation