The following script illustrates the calculation of percent of orders by country on base of all orders. The CONVERTs functions are used to format the percentage figures in currency format.

use Northwind;

go

select

      Country,

      Percentage =

            convert(varchar,convert(money,100.0 * count(*)/

            (select count(*) from Orders)),1)+'%'

from Customers c

join Orders o

on c.CustomerID = o.CustomerID

group by Country

order by count(*) desc

go