Question

我目前正在使用SQL Server 2012并尝试弄清楚如何从CASE语句中获取结果。

所以目前我有一个CASE语句来计算我目前用来查找请求的业务年龄的AgeBusiness字段。这是我的代码：

CASE    WHEN A.[End_Date] > A.[Start_Date] THEN C2.[BUS_DY_OF_CAL_NUM] - C1.[BUS_DY_OF_CAL_NUM] 
        WHEN A.[End_Date] IS NULL and A.[Start_Date] IS NOT NULL THEN C3.[BUS_DY_OF_CAL_NUM] - C1.[BUS_DY_OF_CAL_NUM]
        WHEN A.[End_Date] = A.[Start_Date] THEN 1
END AS AgeBusiness

基本上，如果结束日期大于开始日期，请使用结束日期 - 开始日期进行计算。如果没有结束日期，请使用GETDATE（） - 开始日期进行计算。如果他们是平等的，则为1个工作日。

无论如何，我有这个AgeBusiness字段，并试图使用此字段或此字段中的数据来计算新的Case When语句来计算需求。

在一个完美的世界里，我的CASE陈述会是这样的：

CASE WHEN AgeBusiness >= 0 AND AgeBusiness <11 AND Name = "RequirementA" Then 1 
     WHEN AgeBusiness >= 0 AND AgeBusiness <8 AND Name = "RequirementB" Then 1  
     WHEN AgeBusiness >= 0 AND AgeBusiness <181 AND Name = "RequirementC" Then 1
     WHEN AgeBusiness >= 0 AND AgeBusiness <8 AND Name = "RequirementD" Then 1
     WHEN AgeBusiness >= 0 AND AgeBusiness <11 AND Name = "RequirementE" Then 1
     WHEN AgeBusiness >= 0 AND AgeBusiness <16 AND Name = "RequirementF" Then 1
End AS WithinRequirements

基本上我想创建一个名为Within Requirements的新案例声明，如果它在一定的天数内并且有一个特定的名称，那么它将是，或者在这种情况下1.名称字段已存在于表中我可以参与其中。虽然制作InsideRequirements的要求之一要求AgeBusiness存在，但同时在查询中创建字段......所以这是不可能的。

有没有办法使用上面提到的AgeBusiness中的信息以某种方式创建WithinRequirements？目标是在查询中解决这个问题......即使这意味着冗长的查询。

Answer 1

对中间变量使用CROSS APPLY

SELECT 
CASE WHEN AgeBusiness >= 0 AND AgeBusiness <11 AND Name = "RequirementA" Then 1 
     WHEN AgeBusiness >= 0 AND AgeBusiness <8 AND Name = "RequirementB" Then 1  
     WHEN AgeBusiness >= 0 AND AgeBusiness <181 AND Name = "RequirementC" Then 1
     WHEN AgeBusiness >= 0 AND AgeBusiness <8 AND Name = "RequirementD" Then 1
     WHEN AgeBusiness >= 0 AND AgeBusiness <11 AND Name = "RequirementE" Then 1
     WHEN AgeBusiness >= 0 AND AgeBusiness <16 AND Name = "RequirementF" Then 1
End AS WithinRequirements
FROM  A 
CROSS APPLY (
   SELECT CASE WHEN A.[End_Date] > A.[Start_Date] THEN C2.[BUS_DY_OF_CAL_NUM] - C1.[BUS_DY_OF_CAL_NUM] 
           WHEN A.[End_Date] IS NULL and A.[Start_Date] IS NOT NULL THEN C3.[BUS_DY_OF_CAL_NUM] - C1.[BUS_DY_OF_CAL_NUM]
           WHEN A.[End_Date] = A.[Start_Date] THEN 1
        END AS AgeBusiness
) vars

Answer 2

如果A. [End_Date]为空时，C2。[BUS_DY_OF_CAL_NUM]也为空，你可以像这样重写第一个case语句：

 ABS(COALESCE(COALESCE(C2.[BUS_DY_OF_CAL_NUM],C3.[BUS_DY_OF_CAL_NUM])-C1.[BUS_DY_OF_CAL_NUM],1))

您还在案例陈述中使用BETWEEN并对单个值进行操作，因此重写第二个值，如下所示：

CASE ABS(COALESCE(COALESCE(C2.[BUS_DY_OF_CAL_NUM],C3.[BUS_DY_OF_CAL_NUM])-C1.[BUS_DY_OF_CAL_NUM],1))
     WHEN AgeBusiness >= 0 AND AgeBusiness <11 AND Name = "RequirementA" Then 1 
     WHEN BETWEEN 0 AND 11  AND Name = "RequirementB" Then 1  
     WHEN BETWEEN 0 AND 181 AND Name = "RequirementC" Then 1
     WHEN BETWEEN 0 AND 8   AND Name = "RequirementD" Then 1
     WHEN BETWEEN 0 AND 11  AND Name = "RequirementE" Then 1
     WHEN BETWEEN 0 AND 16  AND Name = "RequirementF" Then 1
End AS WithinRequirements

我相信这个查询不像你原来那么“冗长”。

从以前的SQL Query语句中为CAS查询生成CASE语句

2 个答案: