How To Do Percent/Total in SQL?

Question

I have an typical CUSTOMER/ORDERS set of tables and I want to display the total percentage of sales a particular customer is responsible for. I can get the

Answer 1

select max([order].customerid) customer_id, count(orderid) customer_orders, (select count(orderid) from [order]) as total_orders,
100.0 * (count(orderid))/(select count(orderid) from [order])
from [order] inner join customer
on [order].customerid = customer.customerid
group by [order].customerid

To illustrate the flow, I have included more columns than you need to see in the final result set. Holding the count(order_id) in a temporary variable will be more efficient. I'm not used to postgres, I hope this works with minimal modification.