sql - 按别名分组

Question

我有以下 T-SQL 查询：

select 
    count(CaseId),
    (SELECT DATEDIFF(day,CreateDate,LastActivityDate)) AS DiffDate
from 
    VW_Case_Analysis
where 
    CaseStatus = 'C' 
    and LastActivityDate between '2013-4-1 00:00:00.000' and '2013-4-30 23:59:59.000'
Group By 
    DiffDate

我收到以下错误：

消息 207，级别 16，状态 1，第 15 行
无效的列名称“DiffDate”。

这个查询背后的想法是我想在多少天内得到解决（关闭）的案例数量。

例子：

天

1 = 3 例

2 = 50 例

3 = 20 例

我怎样才能做到这一点？

Answer 1

您需要在子句中使用整个表达式，GROUP BY或者只需将整个语句包装在子查询中，然后对外部语句进行分组。

不能在语句的同一级别上创建ALIAS的子句上使用的原因是，在创建的子句之前执行。GROUP BYSELECTGROUP BYSELECTALIAS

这是 SQL 操作顺序：

• FROM 子句
• WHERE 子句
• GROUP BY 子句
• HAVING 子句
• 选择子句
• ORDER BY 子句

试试这个查询，

SELECT  COUNT(CaseId),
        DiffDate
FROM
        (
            select  CaseId,
                    DATEDIFF(day,CreateDate,LastActivityDate) AS DiffDate
            from    VW_Case_Analysis
            where   CaseStatus = 'C' and 
                    LastActivityDate between '2013-4-1 00:00:00.000' and '2013-4-30 23:59:59.000'
        ) sub
Group By DiffDate

Answer 2

您不能在 group by 子句中使用别名。

要么使用派生表，要么在您的情况下简单地删除第二个 SELECT。

select 
    count(CaseId),
    DATEDIFF(day,CreateDate,LastActivityDate) AS DiffDate
from 
    VW_Case_Analysis
where 
    CaseStatus = 'C' 
    and LastActivityDate between '2013-4-1 00:00:00.000' and '2013-4-30 23:59:59.000'
Group By 
    DATEDIFF(day,CreateDate,LastActivityDate)

Answer 3

这不会给你同样的结果吗？

select  Count(CaseId),
                    DATEDIFF(day,CreateDate,LastActivityDate) AS DiffDate
            from    VW_Case_Analysis
            where   CaseStatus = 'C' and 
                    LastActivityDate between '2013-4-1 00:00:00.000' and '2013-4-30 23:59:59.000'
GROUP BY DATEDIFF(day,CreateDate,LastActivityDate)

我是 SQL 的新手，所以也许我没有正确掌握它。我看到上面的评论有确切的语法，但我不知道它是否正确......

Answer 4

这是实施讨论的一个简单示例

select selectResualt.num ,count(selectResualt.num) as count  
from (select src_num As num from mytable  UNION ALL select dis_num As num from mytable) as selectResualt
group by selectResualt.num
order by count(selectResualt.num) DESC;>

Answer 5

您可以使用CROSS APPLY创建别名并在GROUP BY子句中使用它，如下所示：

select 
    count(CaseId),
    DiffDate
from 
    VW_Case_Analysis
cross apply
    (SELECT DATEDIFF(day,CreateDate,LastActivityDate) AS DiffDate) Alias
where 
    CaseStatus = 'C' 
    and LastActivityDate between '2013-4-1 00:00:00.000' and '2013-4-30 23:59:59.000'
Group By 
    DiffDate