CASE在WHEN子句中使用>>时出现语法错误

Question

当WHEN子句中没有“>”符号时，此查询运行正常，但当ProposalDate比“2017-04”更晚时，我需要此功能-10：00：00：00.000'。不知道为什么当我将WHERE子句添加到>时出现语法错误。

SELECT *, 
    CASE ProposalDate WHEN > '2017-04-10 00:00:00.000' 
     THEN (OrderTotal - ProposalWholesalePrice) + 
      (ProposalWholesalePrice * 1.02) 
     ELSE OrderTotal  
    END "New_OrderTotal" 
FROM webservices.dbo.DT_Open_Orders_Baseprice 
WHERE ProposalSerialNumber = '639036' 

Answer 1

SQL CASEhas two forms表达：

• 简单CASE表达，和
• 搜索到的CASE表达。

简单CASE，即CASE ProposalDate WHEN ...不能与比较运算符一起使用;你需要搜索CASE，而不是：

SELECT 
    * 
, CASE 
     WHEN ProposalDate > '2017-04-10 00:00:00.000' 
     THEN (OrderTotal - ProposalWholesalePrice) + (ProposalWholesalePrice * 1.02) 
     ELSE OrderTotal 
    END "New_OrderTotal" 
FROM webservices.dbo.DT_Open_Orders_Baseprice 
WHERE ProposalSerialNumber = '639036' 

Answer 2

你有没有试过把“WHEN”放在列名之前？ 例如：

SELECT *, CASE WHEN ProposalDate > '2017-04-10 00:00:00.000' 

THEN (OrderTotal - ProposalWholesalePrice) + (ProposalWholesalePrice * 1.02) ELSE OrderTotal 

END "New_OrderTotal" FROM webservices.dbo.DT_Open_Orders_Baseprice WHERE ProposalSerialNumber = '639036' 

Answer 3

速记case语法不使用任何运算符，只是一系列值，其与=条件进行评价。如果你想使用其他运营商，你必须使用完整的case语法：

SELECT *, 
     CASE WHEN ProposalDate > '2017-04-10 00:00:00.000' 
      THEN (OrderTotal - ProposalWholesalePrice) + 
       (ProposalWholesalePrice * 1.02) 
      ELSE OrderTotal 
     END "New_OrderTotal" 
FROM webservices.dbo.DT_Open_Orders_Baseprice 
WHERE ProposalSerialNumber = '639036'