SQL Server：动态数据透视

Question

我发现了很多关于动态透视的文章，首先选择数据，然后运行第二个查询来进行透视，但是我有一个大型查询，我需要动态透视，但不知道如何让它工作。每个主机上的服务器都可以改变这就是为什么我需要它是动态的。可能有一个非常简单的修复方法，但我对 SQL Server 不是很好。

这是我目前的代码：

DECLARE @StartTime Date
DECLARE @EndTime Date

SET @StartTime = '2014-08-19 23:00:00'
SET @EndTime = '2014-08-22 09:21:33.557'

SELECT * 
FROM 
    (SELECT 
        [T1].[AvgMemoryUsage] AS C2, 
        CONVERT(varchar, [T1].[DateTime], 105) AS C3, 
        [T2].[Name] AS C4
     FROM 
        dbo.VIM_VMStatistics AS T1
     INNER JOIN 
        dbo.VIM_VirtualMachineNodes AS T2 ON [T1].[VirtualMachineID] = [T2].[VirtualMachineID]
     INNER JOIN 
        dbo.VIM_HostNodes AS T3 ON [T2].[HostID] = [T3].[HostID]
     LEFT JOIN 
        dbo.Nodes AS T8 ON [T3].[NodeID] = [T8].[NodeID]
     WHERE 
        [T8].[caption] = 'VMWARE-ESX01.Server.Local' 
        AND [T2].[PowerState] = 'poweredOn' 
        AND ([T2].[NodeID] IS NULL) 
        AND [T1].[DateTime] >= @StartTime 
        AND [T1].[DateTime] <= @EndTime

    UNION ALL

    (SELECT 
        [T4].[AvgMemoryUsage] AS C6, 
        CONVERT(varchar, [T4].[DateTime], 105) AS C7, 
        [T5].[Name] AS C8
     FROM 
        dbo.VIM_VMStatistics AS T4
     INNER JOIN 
        dbo.VIM_VirtualMachineNodes AS T5 ON [T4].[VirtualMachineID] = [T5].[VirtualMachineID]
     INNER JOIN 
        dbo.VIM_HostNodes AS T6 ON [T5].[HostID] = [T6].[HostID]
     LEFT JOIN 
        dbo.Nodes AS T7 ON [T5].[NodeID] = [T7].[NodeID]
     WHERE 
        [T6].[NodeID] = 1492 
        AND [T5].[PowerState] = 'poweredOn' 
        AND ([T5].[NodeID] IS NOT NULL) 
        AND [T4].[DateTime] >= @StartTime AND [T4].[DateTime] <= @EndTime)
) AS SourceTable 
PIVOT(
    AVG([c2])
    FOR [C4] IN ([server1],[server2],[server3],[server8],[server12])
) AS PivotTable

Answer 1

如果您已经了解了枢轴的工作原理，那么构建动态枢轴就相当简单了。首先，您需要一个带有分隔列的字符串来进行旋转。为此，您可以使用推荐的FOR XML PATH 和QUOTENAME()：

DECLARE @strPivotColumns nvarchar(max)
SELECT @strPivotColumns = STUFF((SELECT ','  +QUOTENAME([Name]) 
                   FROM dbo.VIM_VirtualMachineNodes FOR XML PATH('')), 1, 1, '')

然后你需要将原始查询保存为字符串，并将字符串与列名连接：

DECLARE @StartTime Date
DECLARE @EndTime Date

SET @StartTime = '2014-08-19 23:00:00'
SET @EndTime = '2014-08-22 09:21:33.557'

DECLARE @DynamicPivotQuery nvarchar(2000)
SET @DynamicPivotQuery = 
'SELECT * FROM (
SELECT [T1].[AvgMemoryUsage] AS C2, CONVERT(varchar, [T1].[DateTime],105) AS C3, [T2].[Name] AS C4
FROM dbo.VIM_VMStatistics AS T1
INNER JOIN dbo.VIM_VirtualMachineNodes AS T2 ON [T1].[VirtualMachineID] = [T2].[VirtualMachineID]
INNER JOIN dbo.VIM_HostNodes AS T3 ON [T2].[HostID] = [T3].[HostID]
LEFT JOIN dbo.Nodes AS T8 ON [T3].[NodeID] = [T8].[NodeID]
WHERE [T8].[caption] = ''VMWARE-ESX01.Server.Local'' AND [T2].[PowerState] = ''poweredOn'' AND ([T2].[NodeID] IS NULL) AND [T1].[DateTime] >= @StartTime AND [T1].[DateTime] <= @EndTime
    UNION ALL
    (
        SELECT [T4].[AvgMemoryUsage] AS C6, CONVERT(varchar, [T4].[DateTime],105) AS C7, [T5].[Name] AS C8
        FROM dbo.VIM_VMStatistics AS T4
        INNER JOIN dbo.VIM_VirtualMachineNodes AS T5 ON [T4].[VirtualMachineID] = [T5].[VirtualMachineID]
        INNER JOIN dbo.VIM_HostNodes AS T6 ON [T5].[HostID] = [T6].[HostID]
        LEFT JOIN dbo.Nodes AS T7 ON [T5].[NodeID] = [T7].[NodeID]
        WHERE [T6].[NodeID] = 1492 AND [T5].[PowerState] = ''poweredOn'' AND ([T5].[NodeID] IS NOT NULL) AND [T4].[DateTime] >= @StartTime AND [T4].[DateTime] <= @EndTime
    )
)AS SourceTable 
PIVOT(
    AVG([c2])
    FOR [C4] IN (' + @strPivotColumns + ')
) AS PivotTable'

然后你可以执行你的查询字符串：

EXEC sp_executesql @DynamicPivotQuery, N'@StartTime date, @EndTime date', @StartTime = @StartTime, @EndTime = @EndTime

由 STEVE 编辑：以下是现在唯一导致引用问题的原因：

FOR [C4] IN (' + @strPivotColumns + ')

错误： 消息 105，第 15 级，状态 1，第 20 行 字符串 'mad-a' 后面的非闭合引号。 消息 102，第 15 级，状态 1，第 20 行 'mad-a' 附近的语法不正确。