> Without incorporating additional meta-data about the purchases onto
> the
> customer table the most basic solution would be:
> SELECT DISTINCT customer_id FROM products WHERE date > (now() - '12
> months'::interval)
> EXCEPT
> SELECT DISTINCT customer_id FROM products WHERE date <= (now() - '12
> months'::interval)
> ---
> Another solution:
> WHERE ... >12 AND NOT EXISTS (SELECT ... WHERE <= 12)
> David J.
subsidiary matter: in what circumstances is better to use EXCEPT and in what NOT EXISTS?
are those equivalents? tried to google their comparison, but no relevant results found for PostgreSQL