CREATE OR REPLACE FUNCTION get_employee_product_changes_last_month()
RETURNS TABLE (
    id BIGINT,
    employee_name TEXT,
    number_of_product_changes BIGINT
)
LANGUAGE plpgsql
AS $$
BEGIN
    RETURN QUERY
    SELECT
        e.id,
        p.name AS employee_name,
        COUNT(DISTINCT mc.date_and_time) AS number_of_product_changes
    FROM employees e
    JOIN personal p
        ON e.id = p.id
    LEFT JOIN makes_change mc
        ON e.id = mc.id
    LEFT JOIN change ch
        ON mc.date_and_time = ch.date_and_time
    WHERE
        mc.date_and_time >= date_trunc('month', CURRENT_DATE) - INTERVAL '1 month'
        AND mc.date_and_time < date_trunc('month', CURRENT_DATE)
    GROUP BY
        e.id,
        p.name
    ORDER BY
        number_of_product_changes DESC;
END;
$$;