为什么我的case语句抛出错误，'='附近的语法不正确？答案

【问题标题】：Why my case statement throws error , incorrect syntax near '='?为什么我的case语句抛出错误，'='附近的语法不正确？
【发布时间】：2014-11-11 04:02:30
【问题描述】：

为什么我的case语句会抛出这个错误：

消息 102，第 15 级，状态 1，第 2 行 '=' 附近的语法不正确。

代码：

Create PROCEDURE [dbo].[Chart_SelectSmsComplaintsValidity]

 @FromDate datetime,
 @ToDate datetime

AS
BEGIN

    Select COUNT(ReceivedMessages.ID) As ReceivedMessageID, 
    CASE ReceivedMessages.IsComplaint WHEN ReceivedMessages.IsComplaint=0 
    THEN 'Incomplete'
    WHEN ReceivedMessages.IsComplaint=1 THEN 'Complete'
    WHEN ReceivedMessages.IsComplaint=-3 THEN 'Inappropriate' END from ReceivedMessages 

    where ReceivedMessages.ReceivedDateTime >= @FromDate AND ReceivedMessages.ReceivedDateTime <= @ToDate
    Group By ReceivedMessages.IsComplaint




END

【问题讨论】：

这是因为您使用的是CASE columnname WHEN columnvalue 形式而不是CASE WHEN expression THEN return WHEN expression THEN return 形式的CASE。只需列出值 1 ，而不是像 IsCompliant=1 这样的完整表达式

标签： sql sql-server tsql

【解决方案1】：

您正在组合CASE 语句的两种不同形式。您可以通过这种方式简化它，因为您在每种情况下都比较相同的表达式：

CASE ReceivedMessages.IsComplaint
  WHEN 0  THEN 'Incomplete'
  WHEN 1  THEN 'Complete'
  WHEN -3 THEN 'Inappropriate' 
END from ReceivedMessages

替代方案是：

CASE
  WHEN ReceivedMessages.IsComplaint=0  THEN 'Incomplete'
  WHEN ReceivedMessages.IsComplaint=1  THEN 'Complete'
  WHEN ReceivedMessages.IsComplaint=-3 THEN 'Inappropriate' 
END

【讨论】：

【解决方案2】：

错误在这一行

CASE ReceivedMessages.IsComplaint WHEN ReceivedMessages.IsComplaint=0

应该是这样的

CASE WHEN ReceivedMessages.IsComplaint=0 THEN 'Incomplete'
WHEN ReceivedMessages.IsComplaint=1 THEN 'Complete'
WHEN ReceivedMessages.IsComplaint=-3 THEN 'Inappropriate' END

【讨论】：