选择未由任何员工订购的产品

Question

我想获取ProductId尚未订购的Employee列表。

我有这个查询，它给了我所有已订购的ProductId，但我想要反过来：

select distinct e.EmployeeID ,p.ProductID from Products p 
  join OrderDetails od on od.ProductID=p.ProductID
 join Orders o on o.OrderID=od.OrderID
 join Employee e on e.EmployeeID=o.EmployeeID order by e.EmployeeID

Answer 1

使用left join并查看NULL：

select distinct e.EmployeeID ,p.ProductID 
from Products p 
   left join OrderDetails od on od.ProductID=p.ProductID
   left join Orders o on o.OrderID=od.OrderID
   left join Employee e on e.EmployeeID=o.EmployeeID 
where e.EmployeeName IS NULL
order by e.EmployeeID

如果Employee表中没有关联的员工记录，则会返回订单详细信息。

修改

试试这个：

 select e1.EmployeeID,p1.ProductID
 from Employee e1, p1.ProductID
 where e1.EmployeeID NOT IN
 ( select distinct e.EmployeeID from Products p 
   join OrderDetails od on od.ProductID=p.ProductID
   join Orders o on o.OrderID=od.OrderID
   join Employee e on e.EmployeeID=o.EmployeeID)
 and p1.ProductID NOT IN 
 ( select distinct p.ProductID from Products p 
   join OrderDetails od on od.ProductID=p.ProductID
   join Orders o on o.OrderID=od.OrderID
   join Employee e on e.EmployeeID=o.EmployeeID)

如果您提供一些示例数据和表格结构，我们可以进行更好的查询。

Answer 2

试一试 -

select distinct e.EmployeeID ,p.ProductID 
from Products p 
join OrderDetails od on od.ProductID=p.ProductID 
join Orders o on o.OrderID=od.OrderID 
left join Employee e on e.EmployeeID=o.EmployeeID 
where e.EmployeeID is null
order by o.EmployeeID;