Question

我有一张包含以下内容的表格：

ID   Node   LoadTime   DateTimeCST   Failed
-----------------------------------------

我正在尝试编写一个返回下表的查询（Node是DISTINCT）。

Node    TodaysAverageLoadTime    HistoricalLoadTime
----------------------------------------------------

所以，我基本上试图在过去的24小时内取平均值的LoadTime，然后是LoadTime的另一个平均值，它平均表示LoadTime表中的所有数据。这是我用来获得今天平均值的查询。

SELECT DISTINCT Node, AVG(LoadTime)
FROM dbo.Table
WHERE Failed != 1
AND DATEDIFF(day, DateTimeCST, GETDATE()) = 0 
GROUP BY Node

我需要添加到此查询中以平均所有记录的LoadTime？任何帮助将不胜感激。谢谢。

Answer 1

由于标识TodaysAverageLoadTime和HistoricalLoadTime记录的标准不同，因此无法在单个查询中完成。但你可以按如下方式模拟它：

SELECT 
       Node,
       ISNULL(TodaysAvgLoadTime, 0)
       ISNULL(HistoricalLoadTime, 0)
FROM 
        (
            SELECT 
                 Node, 
                 AVG(LoadTime) 'TodaysAvgLoadTime'
            FROM 
                 dbo.Table
            WHERE 
                 Failed != 1
            AND  DATEDIFF(day, DateTimeCST, GETDATE()) = 0 
            GROUP BY Node
        ) AS A
        FULL OUTER JOIN
        (
            SELECT 
                 Node, 
                 AVG(LoadTime) 'HistoricalLoadTime'
            FROM 
                 dbo.Table
            WHERE 
                 Failed != 1
            GROUP BY Node
        ) AS B
        ON A.Node = B.Node

Answer 2

您可以使用多个子查询来获取数据以及跨数据的连接。如下所示：

SELECT Node, t1.avg, t2.avg FROM
    (SELECT DISTINCT Node, AVG(LoadTime) AS avg
    FROM dbo.Table, 
    WHERE Failed != 1
    AND DATEDIFF(day, DateTimeCST, GETDATE()) = 0 
    GROUP BY Node) t1, 
    (SELECT DISTINCT Node, AVG(LoadTime) AS avg
    FROM dbo.Table, 
    WHERE Failed != 1
    GROUP BY Node) t2
WHERE t1.node = t2.node

在一个查询中对列进行两次平均

2 个答案: