Question

我在下方查询了=＆gt;

SELECT FirstName,
       LastName,
       COUNT(*) AantalBestellingen,
       YEAR(Orders.OrderDate) as Jaar
from Employees 
    RIGHT JOIN Orders ON (Employees.EmployeeID=Orders.EmployeeID) 
WHERE Employees.ReportsTo IS NOT NULL 
GROUP BY Employees.FirstName, Employees.LastName, YEAR (Orders.OrderDate)
ORDER BY YEAR (Orders.OrderDate)

我需要选择员工的名字，姓氏以及他们去年处理的总订单。

在查询中按年份添加组后，它不再显示唯一的员工，但会显示年份。我只需要获得独特的员工以及他们处理订单的最后一个订单年度。

我有什么建议我做错了吗？

Answer 1

一种方法是使用内部选择：

SELECT 
  FirstName, 
  LastName, 
  COUNT(*) as AantalBestellingen, 
  (select YEAR(max(Orders.OrderDate)) from Orders O 
      where Employees.EmployeeID=O.EmployeeID) as Jaar 
from 
  Employees 
  RIGHT JOIN Orders 
    ON (Employees.EmployeeID=Orders.EmployeeID) 
  WHERE 
    Employees.ReportsTo IS NOT NULL 
GROUP BY 
  Employees.FirstName, 
  Employees.LastName
ORDER BY Jaar

Answer 2

您可以将Last Year条件放在WHERE子句中，如下所示

SELECT FirstName,
       LastName,
       COUNT(*) AantalBestellingen,
from Employees 
    RIGHT JOIN Orders ON (Employees.EmployeeID=Orders.EmployeeID) 
WHERE Employees.ReportsTo IS NOT NULL AND YEAR(Orders.OrderDate) = 2014
GROUP BY Employees.FirstName, Employees.LastName

Answer 3

你能试试这个......这将给所有员工，他去年唯一的订单和去年。

;with cteMaxYear as
(select max(YEAR(Orders.OrderDate)) MaxOrderYear, EmployeeID 
from Orders 
group by EmployeeID)

SELECT FirstName,
       LastName,
       COUNT(*) AantalBestellingen,
       m.MaxOrderYear as Jaar
from Employees e
left outer join cteMaxYear m
    inner join Orders o ON m.EmployeeID=o.EmployeeID and m.MaxOrderYear=o.YEAR(Orders.OrderDate)
    on e.EmployeeID = m.EmployeeID
WHERE e.ReportsTo IS NOT NULL 
GROUP BY e.FirstName, e.LastName, m.MaxOrderYear
ORDER BY  m.MaxOrderYear

SQL GROUP BY FirstName，Lastname和Year

3 个答案: