从不订购的客户
select c.Name as Customers from Customers c left join Orders o on c.Id = o.CustomerId where o.CustomerId is null
select customers.name customers from customers where customers.id not in (select orders.customerid from orders)
从不订购的客户
select c.Name as Customers from Customers c left join Orders o on c.Id = o.CustomerId where o.CustomerId is null
select customers.name customers from customers where customers.id not in (select orders.customerid from orders)