part_1_tema_2_lesson_17_task_6

WITH
 pz AS (SELECT *,
               DATE_TRUNC('month', created_at)::date AS month_of_costs,
               SUM(costs) OVER (
                                ORDER BY DATE_TRUNC('month', created_at)) AS total_amt
        FROM tools_shop.costs)

SELECT DISTINCT month_of_costs, total_amt
FROM pz
WHERE EXTRACT(
              YEAR FROM month_of_costs) IN (2017,2018)