如何从SQL Server中的表中查询Xml值和属性？

Question

我有一个包含Xml列的表:

SELECT * 
FROM Sqm

xml一行数据的样本将是:

<Sqm version="1.2">
  <Metrics>
    <Metric id="TransactionCleanupThread.RecordUsedTransactionShift" type="timer" unit="µs" count="1" sum="21490"   average="21490"   minValue="73701"    maxValue="73701"                               >73701</Metric>
    <Metric id="TransactionCleanupThread.RefundOldTrans"             type="timer" unit="µs" count="1" sum="184487"  average="184487"  minValue="632704"   maxValue="632704"                              >632704</Metric>
    <Metric id="Database.CreateConnection_SaveContextUserGUID"       type="timer" unit="µs" count="2" sum="7562"    average="3781"    minValue="12928"    maxValue="13006"    standardDeviation="16"     >12967</Metric>
    <Metric id="Global.CurrentUser"                                  type="timer" unit="µs" count="6" sum="4022464" average="670411"  minValue="15"       maxValue="13794345" standardDeviation="1642047">2299194</Metric>
    <Metric id="Global.CurrentUser_FetchIdentityFromDatabase"        type="timer" unit="µs" count="1" sum="4010057" average="4010057" minValue="13752614" maxValue="13752614"                            >13752614</Metric>
  </Metrics>
</Sqm>

对于这些数据,我希望:

SqmId  id                                                   type   unit  count  sum      minValue  maxValue  standardDeviation  Value
=====  ===================================================  =====  ====  =====  ======   ========  ========  =================  ======
1      TransactionCleanupThread.RecordUsedTransactionShift  timer  µs    1      21490    73701     73701     NULL               73701
1      TransactionCleanupThread.RefundOldTrans              timer  µs    1      184487   632704    632704    NULL               632704
1      Database.CreateConnection_SaveContextUserGUID        timer  µs    2      7562     12928     13006     16                 12967
1      Global.CurrentUser                                   timer  µs    6      4022464  15        13794345  1642047            2299194
1      Global.CurrentUser_FetchIdentityFromDatabase         timer  µs    1      4010057  13752614  13752614  NULL               13752614
2      ...

最后,我需要实际执行SUM(),MIN(),MAX()聚集.但是现在我只是想查询一个xml列.

在伪代码中,我会尝试类似:

SELECT
    SqmId,
    Data.query('/Sqm/Metrics/Metric/@id') AS id,
    Data.query('/Sqm/Metrics/Metric/@type') AS type,
    Data.query('/Sqm/Metrics/Metric/@unit') AS unit,
    Data.query('/Sqm/Metrics/Metric/@sum') AS sum,
    Data.query('/Sqm/Metrics/Metric/@count') AS count,
    Data.query('/Sqm/Metrics/Metric/@minValue') AS minValue,
    Data.query('/Sqm/Metrics/Metric/@maxValue') AS maxValue,
    Data.query('/Sqm/Metrics/Metric/@standardDeviation') AS standardDeviation,
    Data.query('/Sqm/Metrics/Metric') AS value
FROM Sqm

但该SQL查询不起作用:

消息2396,级别16,状态1,行2
XQuery [Sqm.data.query()]:属性可能不会出现在元素之外

我已经找到了,并且令人惊讶的是,Xml查询的文档记录很少或者说是例如.大多数资源而不是查询表,查询变量 ; 我没做的.大多数资源仅使用xml查询进行过滤和选择,而不是读取值.大多数资源读取硬编码子节点(按索引),而不是实际值.

我读过的相关资源

• /sf/ask/67650901/
• SQL Server查询元素值的xml属性
• SQL查询XML属性
• SQL Server 2005 XQuery和XML-DML - 第1部分
• BOL:Microsoft SQL Server 2005中的XML支持
• 在SQL Server中查询XML
• 基本SQL Server XML查询
• BOL:query()方法(xml数据类型)
• XML Workshop V - 从XML列读取值
• SQL SERVER - 发现XML数据类型方法简介 - 入门

更新:.value而不是.query

我试着随机使用.value,代替.query:

SELECT
    Sqm.SqmId,
    Data.value('/Sqm/Metrics/Metric/@id', 'varchar(max)') AS id,
    Data.value('/Sqm/Metrics/Metric/@type', 'varchar(max)') AS type,
    Data.value('/Sqm/Metrics/Metric/@unit', 'varchar(max)') AS unit,
    Data.value('/Sqm/Metrics/Metric/@sum', 'varchar(max)') AS sum,
    Data.value('/Sqm/Metrics/Metric/@count', 'varchar(max)') AS count,
    Data.value('/Sqm/Metrics/Metric/@minValue', 'varchar(max)') AS minValue,
    Data.value('/Sqm/Metrics/Metric/@maxValue', 'varchar(max)') AS maxValue,
    Data.value('/Sqm/Metrics/Metric/@standardDeviation', 'varchar(max)') AS standardDeviation,
    Data.value('/Sqm/Metrics/Metric', 'varchar(max)') AS value
FROM Sqm

但这也行不通:

消息2389,级别16,状态1,行3 XQuery [Sqm.data.value()]:
'value()'需要单例(或空序列),找到类型为'xdt:untypedAtomic*'的操作数

Answer 1

实际上你接近你的目标,你只需要使用nodes()方法来分割你的行,然后获取值:

select
    s.SqmId,
    m.c.value('@id', 'varchar(max)') as id,
    m.c.value('@type', 'varchar(max)') as type,
    m.c.value('@unit', 'varchar(max)') as unit,
    m.c.value('@sum', 'varchar(max)') as [sum],
    m.c.value('@count', 'varchar(max)') as [count],
    m.c.value('@minValue', 'varchar(max)') as minValue,
    m.c.value('@maxValue', 'varchar(max)') as maxValue,
    m.c.value('.', 'nvarchar(max)') as Value,
    m.c.value('(text())[1]', 'nvarchar(max)') as Value2
from sqm as s
    outer apply s.data.nodes('Sqm/Metrics/Metric') as m(c)

sql fiddle demo

Answer 2

使用value而不是query(必须指定要在XQuery中返回的节点索引以及将sql数据类型作为第二个参数返回):

select
    xt.Id
    , x.m.value( '@id[1]', 'varchar(max)' ) MetricId
from
    XmlTest xt
    cross apply xt.XmlData.nodes( '/Sqm/Metrics/Metric' ) x(m)

Answer 3

我不明白为什么有些人建议使用cross apply或outer apply将xml转换为值表.对我来说,这只会带来太多的数据.

这是我如何创建xml对象,然后将其转换为表格的示例.

(我在我的xml字符串中添加了空格,只是为了更容易阅读.)

DECLARE @str nvarchar(2000)

SET @str = ''
SET @str = @str + '<users>'
SET @str = @str + '  <user>'
SET @str = @str + '     <firstName>Mike</firstName>'
SET @str = @str + '     <lastName>Gledhill</lastName>'
SET @str = @str + '     <age>31</age>'
SET @str = @str + '  </user>'
SET @str = @str + '  <user>'
SET @str = @str + '     <firstName>Mark</firstName>'
SET @str = @str + '     <lastName>Stevens</lastName>'
SET @str = @str + '     <age>42</age>'
SET @str = @str + '  </user>'
SET @str = @str + '  <user>'
SET @str = @str + '     <firstName>Sarah</firstName>'
SET @str = @str + '     <lastName>Brown</lastName>'
SET @str = @str + '     <age>23</age>'
SET @str = @str + '  </user>'
SET @str = @str + '</users>'

DECLARE @xml xml
SELECT @xml = CAST(CAST(@str AS VARBINARY(MAX)) AS XML) 

--  Iterate through each of the "users\user" records in our XML
SELECT 
    x.Rec.query('./firstName').value('.', 'nvarchar(2000)') AS 'FirstName',
    x.Rec.query('./lastName').value('.', 'nvarchar(2000)') AS 'LastName',
    x.Rec.query('./age').value('.', 'int') AS 'Age'
FROM @xml.nodes('/users/user') as x(Rec)

这是输出:

Answer 4

我一直在尝试做一些非常相似但没有使用节点的东西.但是,我的xml结构有点不同.

你有这样的:

<Metrics>
    <Metric id="TransactionCleanupThread.RefundOldTrans" type="timer" ...>

如果是这样的话:

<Metrics>
    <Metric>
        <id>TransactionCleanupThread.RefundOldTrans</id>
        <type>timer</type>
        .
        .
        .

然后你可以简单地使用这个SQL语句.

SELECT
    Sqm.SqmId,
    Data.value('/Sqm/Metrics/Metric/id)[1]', 'varchar(max)') as id,
    Data.value('/Sqm/Metrics/Metric/type)[1]', 'varchar(max)') AS type,
    Data.value('/Sqm/Metrics/Metric/unit)[1]', 'varchar(max)') AS unit,
    Data.value('/Sqm/Metrics/Metric/sum)[1]', 'varchar(max)') AS sum,
    Data.value('/Sqm/Metrics/Metric/count)[1]', 'varchar(max)') AS count,
    Data.value('/Sqm/Metrics/Metric/minValue)[1]', 'varchar(max)') AS minValue,
    Data.value('/Sqm/Metrics/Metric/maxValue)[1]', 'varchar(max)') AS maxValue,
    Data.value('/Sqm/Metrics/Metric/stdDeviation)[1]', 'varchar(max)') AS stdDeviation,
FROM Sqm

对我来说,这比使用外部申请或交叉申请要困难得多.

我希望这可以帮助其他人寻找更简单的解决方案!