sql - 检索扩展事件 session 环缓冲区中死锁的时间戳

Question

我正在尝试查询 system_health用于死锁事件的扩展事件环形缓冲区。到目前为止，我已经得到了如下所示的死锁图。对于缺乏引用，我深表歉意；我丢失了找到此查询的页面:

SELECT 
    CAST(event_data.value('(event/data/value)[1]', 'nvarchar(max)') AS XML) AS DeadlockGraph
FROM 
(   SELECT XEvent.query('.') AS event_data 
    FROM 
    (   -- Cast the target_data to XML 
        SELECT CAST(target_data AS XML) AS TargetData 
        FROM sys.dm_xe_session_targets AS st 
        INNER JOIN sys.dm_xe_sessions AS s 
            ON s.address = st.event_session_address 
        WHERE name = N'system_health' 
          AND target_name = N'ring_buffer' 
    ) AS Data 
    -- Split out the Event Nodes 
    CROSS APPLY TargetData.nodes ('RingBufferTarget/event[@name="xml_deadlock_report"]') AS XEventData (XEvent)   
) AS tab (event_data);

我还想包含一列用于显示这些事件的时间戳。如果我运行内部查询，我会看到事件的时间戳位于事件本身的 XML 中:

<event name="xml_deadlock_report"
    package="sqlserver" id="123" version="1"
    timestamp="2013-07-23T16:25:25.495Z">

如何解析这个时间戳并显示它？我在使用 TSQL 解析 XML 方面的经验有限。

我已经尝试过这个:

SELECT
    CAST(event_data.value('/@timestamp', 'nvarchar(500)') AS datetime) AS [time],
    CAST(event_data.value('(event/data/value)[1]', 'nvarchar(max)') AS XML) AS DeadlockGraph

但我收到错误:

Msg 2390, Level 16, State 1, Line 2 XQuery [tab.event_data.value()]: Top-level attribute nodes are not supported

这个:

CAST(event_data.value('(event/@timestamp)', 'nvarchar(500)') AS datetime) AS [time],

产生此错误:

Msg 2389, Level 16, State 1, Line 2 XQuery [tab.event_data.value()]: 'value()' requires a singleton (or empty sequence), found operand of type 'xdt:untypedAtomic *'

Answer 1

改变这个

CAST(event_data.value('(event/@timestamp)', 'nvarchar(500)') AS datetime) AS [time],

有了这个

SELECT 
    event_data.value('(/event/@timestamp)[1]','VARCHAR(50)') AS TS1,
    event_data.value('(/event/@timestamp)[1]','DATETIMEOFFSET') AS TS2,
    ...

结果:

TS1                      TS2                               
------------------------ ----------------------------------
2013-07-23T17:49:46.072Z 2013-07-23 17:49:46.0720000 +00:00