Obtener un listado de cual fue el volumen de ventas (cantidad) por año y método de envío mostrando para cada registro, qué porcentaje representa del total del año. Resolver utilizando Subconsultas y Funciones Ventana, luego comparar la diferencia en la demora de las consultas.

select year, shipping_mode, sum(quantity) as total_year, (sum(quantity) / sum(sum(quantity)) over (partition by year)) as percent
from sales
group by year, shipping_mode
order by year, total_year desc;


with total_year as (
    select year, sum(quantity) as total_year
    from sales
    group by year
)
select year, shipping_mode, quantity, (quantity / total_year) as percent
from sales left join total_year using (year)
order by year, quantity desc;