SQL第二个Case语句关闭第一个Case语句'；s柱

我正在编写一个带有两个Case-When语句的查询，第二个语句使用第一个语句的状态来确定值。但是，我在第2条语句中得到一个无效列错误。有人知道解决这个问题的简单方法吗？谢谢

select 
    a.ID
    ,ss.Date
    ,ss.Name
    ,ss.Payload
    ,case when statusdescription = 'Bad Request' then 'Not Resolved' Else 'Resolved' End as [Error Status] 
    ,case when 
    [Error Status] = 'Not Resolved' --Invalid Column issue occurring with [Error Status] here
    then 'No Resolution' Else a.Date End as [Date],
    ,GETDATE() [Insert Date]

from #Errors a
join Table1 ss on a.id = ss.Id and a.Date = ss.Date 
order by a.Date desc

---

我将第一个case表达式嵌套在第二个case表达式中

select 
a.ID
,ss.Date
,ss.Name
,ss.Payload
,case when statusdescription = 'Bad Request' then 'Not Resolved' Else 'Resolved' End as [Error Status] 
,case when 
case when statusdescription = 'Bad Request' then 'Not Resolved' Else 'Resolved' End = 'Not Resolved' --Invalid Column issue occurring with [Error Status] here
then 'No Resolution' Else a.Date End as [Date],
,GETDATE() [Insert Date]

from #Errors a
join Table1 ss on a.id = ss.Id and a.Date = ss.Date 
order by a.Date desc

---

在第二个

案例

表达式中，您只需再次检查

statusdescription

的值：

SELECT 
    a.ID,
    ss.Date,
    ss.Name,
    ss.Payload,
    CASE WHEN statusdescription = 'Bad Request'
         THEN 'Not Resolved' ELSE 'Resolved' END AS [Error Status], 
    CASE WHEN statusdescription = 'Bad Request'
         THEN 'No Resolution' ELSE a.Date END AS [Date],
    GETDATE() AS [Insert Date]
FROM #Errors a
INNER JOIN Table1 ss
    ON a.id   = ss.Id   AND
       a.Date = ss.Date 
ORDER BY a.Date DESC

请注意，如果此查询未运行，您可能必须将

a.Date

转换为第二个

CASE

表达式中的文本。

CASE表达式，而不是语句…我刚刚做了一个自己的测试（Sql Server 2014），并且我能够从后面的一个CASE列引用前面的CASE列，因此这是可能的（在Sql Server 2014中）。

select 
a.ID
,ss.Date
,ss.Name
,ss.Payload
,case when statusdescription = 'Bad Request' then 'Not Resolved' Else 'Resolved' End as [Error Status] 
,case when 
case when statusdescription = 'Bad Request' then 'Not Resolved' Else 'Resolved' End = 'Not Resolved' --Invalid Column issue occurring with [Error Status] here
then 'No Resolution' Else a.Date End as [Date],
,GETDATE() [Insert Date]

from #Errors a
join Table1 ss on a.id = ss.Id and a.Date = ss.Date 
order by a.Date desc