Estoy tratando de ejecutar una consulta uniendo 2 grandes conjuntos de datos y estoy golpeando los recursos excedidos durante el error de ejecución de la consulta. He leído que existen soluciones al usar Unir cada y Grupo, pero no lo que serían esas soluciones.

SELECT 
  year(users.firstseen) as first_year,
  month(users.firstseen) as first_month, 
  DATEDIFF(orders.timestamp,users.firstseen) as days_elapsed,
  count(orders.user_key) as count_orders
FROM 
  [project.orders] as orders
JOIN EACH
  [project.users] AS users
ON
  orders.user_key = users.user_key
WHERE orders.store = 'ios'
GROUP EACH BY 1,2,3

Edición: funcionó lo siguiente:

SELECT
  year(users.firstseen) as firstyear,
  month(users.firstseen) as firstmonth,
  DATEDIFF(orders.timestamp, users.firstseen) as days_elapsed,
  COUNT(users.firstseen) AS count_orders FROM [project.orders] as orders
JOIN EACH( SELECT user_key, firstseen FROM [project.users]
WHERE store_key = 'ios') as users ON orders.user_key = users.user_key
GROUP BY firstyear, firstmonth, days_elapsed
ORDER BY firstyear, firstmonth, days_elapsed