MySQL 使用 Sum 和 Case

Question

我正在尝试使用连接到 MySQL 数据库的 ASP.NET 创建一个 GridView。数据如下所示。

BusinessUnit    OrderDate      Canceled
UnitA           1/15/2013          N
UnitA           10/1/2013          N
UnitB           10/15/2013         N
UnitB           10/22/2013         N
UnitB           10/22/2013         N

根据上面的记录，我希望结果如下所示

BusinessUnit  TodaysOrders   ThisMonthsOrders  ThisYearsOrders
UnitA              0                1                2
UnitB              2                3                3

我当前的代码如下。它给我错误(关于 DatabaseName.sum 的东西不存在。检查函数名称解析和解析”部分...)

Select  
    SUM (CASE WHEN (OrderDate)=DATE(NOW()) THEN 1 ELSE 0 END) AS TodaysOrders,
    SUM (CASE WHEN YEAR(OrderDate) = YEAR(CURDATE()) AND MONTH(OrderDate) = MONTH(CURDATE()) THEN 1 ELSE 0 END) AS ThisMonthsOrders,
    SUM (CASE WHEN YEAR(main_order_managers.creation_date) = YEAR(CURDATE()) THEN 1 ELSE 0 END) AS ThisYearsOrders 

代码继续

FROM OrderTable WHERE OrderTable.Canceled. <> 'Y';

在这里 Sum Case 是最好的用法吗？

Answer 1

该错误是由函数名和括号之间的空格引起的

SUM (CASE WHEN ...
   ^^

阅读更多 Function Name Parsing and Resolution

试试

SELECT BusinessUnit,
       SUM(CASE WHEN OrderDate = CURDATE() THEN 1 ELSE 0 END) TodaysOrders,
       SUM(CASE WHEN DATE_FORMAT(OrderDate, '%Y%m') = DATE_FORMAT(CURDATE(), '%Y%m') THEN 1 ELSE 0 END) ThisMonthsOrders,
       SUM(CASE WHEN YEAR(OrderDate) = YEAR(CURDATE()) THEN 1 ELSE 0 END) ThisYearsOrders
  FROM OrderTable
 WHERE Canceled <> 'Y'
 GROUP BY BusinessUnit

这里是 SQLFiddle 演示