Question

我遇到了一个问题，我已经放在一起了，我已经按照http://www.sql-server-helper.com/error-messages/msg-147.aspx（页面底部）的说明进行操作了，我看不出我的代码与示例有什么不同除了WHERE子句和内部联接。

但我仍然收到以下错误：

Msg 147，Level 15，State 1，Line 5
聚合可能不会出现在WHERE子句中，除非它位于HAVING子句或选择列表中包含的子查询中，并且要聚合的列是外部引用。

这是我自己的代码：

SELECT  *
FROM    [dbo].[mail] AS rm
    INNER JOIN [dbo].[mytbl] AS ec ON [rm].[webref] = [ec].[Webref]
WHERE   rm.[webref] = 'XYZ-594112'
    AND [PolRef@] = ( SELECT    MAX([PolRef@])
                      FROM      [dbo].[mytbl]
                    )

任何人都可以解释为什么会发生这种情况吗？

编辑：

CREATE TABLE [dbo].[mail](
[id] [int] IDENTITY(1,1) NOT NULL,
[date] [datetime] NULL,
[webref] [nvarchar](20) NULL
) ON [PRIMARY]

另一个表实际上是一个由几个其他表组成的视图，但是减少的版本将是：

CREATE TABLE [dbo].[mytbl](
[PolRef@] [varchar](10) NULL,
[Webref] [varchar](30) NULL) ON [PRIMARY]

编辑更新：

现在收到以下错误：

SELECT  *
FROM    [FreshSystems].[dbo].[mail] AS rm
    INNER JOIN [dbo].[mytbl] AS ec ON [rm].[webref] = [ec].[Webref]
WHERE   rm.[webref] = 'XYZ-594112'
HAVING [PolRef@] = ( SELECT    MAX([PolRef@])
                      FROM      [dbo].[mytbl]
                    )

错误

Msg 8121, Level 16, State 1, Line 5
Column 'mytbl.PolRef@' is invalid in the HAVING clause because it is not     contained in either an aggregate function or the GROUP BY clause.

WORKING：

SELECT  *
FROM    [dbo].[mail] AS rm
LEFT OUTER JOIN  [dbo].[mytbl] AS ec ON [rm].[webref] = [ec].[Webref]
WHERE   rm.[webref] = 'XYZ-594112'
AND [PolRef@] = ( SELECT    MAX([PolRef@])
                  FROM      [dbo].[mytbl]
                  WHERE [Webref] = 'XYZ-594112'
                )

Answer 1

我会用这样的东西

select  *
from    [dbo].[mail] as rm
join    [dbo].[mytbl] as ec
on      [rm].[webref] = [ec].[webref]
join    ( select    max([polref@]) y
          from      [dbo].[mail]
        ) x
on      [polref@] = x.y
where   rm.[webref] = 'xyz-594112'

Answer 2

只需按poltef@ desc排序，然后选择前1：

SELECT TOP 1 * WITH TIES
FROM mail rm
JOIN mytbl ec ON rm.webref = ec.Webref
WHERE rm.webref = 'XYZ-594112'
ORDER BY poltef@ desc

另外，我删除了所有不必要的字符。

Answer 3

工作代码：

SELECT  *
FROM    [dbo].[mail] AS rm
LEFT OUTER JOIN  [dbo].[mytbl] AS ec ON [rm].[webref] = [ec].[Webref]
WHERE   rm.[webref] = 'XYZ-594112'
AND [PolRef@] = ( SELECT    MAX([PolRef@])
                  FROM      [dbo].[mytbl]
                  WHERE [Webref] = 'XYZ-594112'
                )

WHERE ID = MAX（ID）可能不会出现错误聚合

3 个答案: