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我有一个包含一些列的表：

WON   param      |  machine   |    inputdate     |  val
---|-------------|------------|------------------|--------|
18 | PAR.SPTDM.X1|    MM01    | 20/01/2013 12:43 |  2.5   |
18 | PAR.SPTDM.Y1|    MM01    | 20/01/2013 12:43 |  3,4   |
22 | PAR.SPTDM.X1|    MM01    | 22/01/2013 16:10 |  1.2   |
22 | PAR.SPTDM.Y1|    MM01    | 22/01/2013 16:10 |  1.7   |
33 | PAR.SPTDM.X1|    MM03    | 22/01/2013 16:13 |  2.34  |
33 | PAR.SPTDM.Y1|    MM03    | 22/01/2013 16:13 |  2,21  |
27 | PAR.LAS.PWR |    MM10    | 25/01/2013 08:14 |  100.5 |
14 | PAR.LAS.UV  |    MM10    | 18/01/2013 17:27 |  134.8 |
41 | PAR.LAS.UV  |    SLA4    | 27/01/2013 09:14 |  2,1   |
62 | PAR.LAS.UV  |    SLA5    | 27/01/2013 11:15 |  14.6  |

其中一些行被重复（由于我不知道的原因，它是管理系统的后端）。该value列也是一个字符串，它需要转换为数字。

数据库是只读的，我想根据几个条件将数据拉入 Excel 工作表：

  • 分组machine和param
  • 过滤param：仅'PAR.SPTDM.%'
  • 过滤machine：仅'MM%'
  • 用逗号忽略 val，将其余部分转换为数字

使用以下查询可以正常工作：

SELECT DISTINCT t1.param, t1.machine, cast(t1.val as float), t1.inputdate
FROM dbbackend t1
WHERE (t1.machine Like 'MM%')
    AND (t1.param Like 'PAR.SPTDM.%')
    AND (t1.val<>'') And (t1.val not Like '%,%')

现在我只想用最新的inputdate. 首先我试过

SELECT DISTINCT t1.param, t1.machine, max(cast(t1.val as float)), max(t1.inputdate)
FROM dbbackend t1
WHERE (t1.machine Like 'MM%')
    AND (t1.param Like 'PAR.SPTDM.%')
    AND (t1.val<>'') And (t1.val not Like '%,%')
GROUP BY machine, param

但这给了我val不在数据集中的，正确的机器/参数/输入日期，但错误的 val。

下一次尝试是

SELECT DISTINCT t1.param, t1.machine, cast(t1.val as float), t1.inputdate
FROM dbbackend t1
WHERE t1.WON IN
    (
    SELECT latestrec.WON FROM (
        SELECT DISTINCT max(t2.WON), t2.param, t2.machine, max(t2.inputdate)
        FROM dbbackend t2
        WHERE (t2.machine Like 'MM%')
            AND (t2.param Like 'PAR.SPTDM.%')
            AND (t2.val<>'') And (t2.val not Like '%,%')
            GROUP BY machine, param
        ) as latestrec
    )

但这行不通，MS Query 告诉我

无法添加表“（”。

那么有人可以告诉我为什么我在第一次调用时得到错误的值，为什么第二次不起作用，或者正确的方法是什么？我还怀疑 MS 查询会跳过该嵌套子查询：/

4

1 回答 1

3

你可以试试这个CTE功能ROW_NUMBER：

WITH x AS (SELECT t1.param, 
                t1.machine, 
                Cast(t1.val AS FLOAT) AS val, 
                t1.inputdate, 
                RN=Row_number() 
                     OVER( 
                       partition BY t1.machine, t1.param 
                       ORDER BY t1.inputdate DESC) 
         FROM   dbbackend t1 
         WHERE  ( t1.machine LIKE 'MM%' ) 
                AND ( t1.param LIKE 'PAR.SPTDM.%' ) 
                AND ( t1.val <> '' ) 
                AND ( t1.val NOT LIKE '%,%' )) 
SELECT param, 
       machine, 
       val, 
       inputdate 
FROM   x 
WHERE  rn = 1
于 2013-01-28T11:59:45.447 回答