我只是做了一个小测试。随着 .nodes（），你可以得到一些3％...不是真的很多实际。在我的测试机（只是一个简单的笔记本电脑），我得到了一个结果出来〜5秒内100.000行。不是说不好，其实...如果你想它速度快，你必须让搜索值了XML，或者你使用XML索引：

I just did a little test. With .nodes() you could get some 3%... Not really much actually. In my test machine (just a simple laptop) I got a result out of 100.000 rows within ~5 seconds. Not that bad in fact... If you want it fast, you'll have to get the search values out of the XML or you use an XML index:

首先，我创建一个测试表和100.000行填充它。一个随机数（0到1000）应导致〜100行的每个随机数。这个数字被放入一个varchar山坳的和的作为值到您的XML。

First I create a test table and fill it with 100.000 rows. A random number (0 to 1000) should lead to ~100 rows for each random number. This number is put into a varchar col and as a value into your XML.

然后我做一个电话像你需要它 .exist（）和 .nodes（）与第二小的优势，但都需要5到6秒。
其实我做的通话两次：在交换秩序，略有改变搜索PARAMS和以//项目，而不是完整路径，第二次通过缓存的结果或计划，以避免误报

Then I do a call like you'd need it with .exist() and with .nodes() with a small advantage for the second, but both take 5 to 6 seconds. In fact I do the calls twice: a second time in swapped order and with slightly changed search params and with "//item" instead of the full path to avoid false positives via cached results or plans.

现在 - 什么样的真正的也让我感到吃惊！ - 在 .nodes 是完整路径为多较前（9秒），但 .exist（）已经降到了半秒，完整路径甚至下降到约0.10秒

Now - what really did surprise me! - the .nodes with full path is much slower than before (9 secs) but the .exist() is down to half a second, with full path even down to about 0.10 sec

和这里的code为copy'n'paste和自我测试

And here's the code for copy'n'paste and self testing

CREATE TABLE #testTbl(ID INT IDENTITY PRIMARY KEY, SomeData VARCHAR(100),XmlColumn XML);
GO

DECLARE @RndNumber VARCHAR(100)=(SELECT CAST(CAST(RAND()*1000 AS INT) AS VARCHAR(100)));

INSERT INTO #testTbl VALUES('Data_' + @RndNumber,
'<error application="application" host="host" type="exception" message="message" >
  <serverVariables>
    <item name="name1">
      <value string="text" />
    </item>
    <item name="name2">
      <value string="text2" />
    </item>
    <item name="name3">
      <value string="text3" />
    </item>
    <item name="name4">
      <value string="text4" />
    </item>
    <item name="name5">
      <value string="My test ' +  @RndNumber + '" />
    </item>
    <item name="name6">
      <value string="text6" />
    </item>
    <item name="name7">
      <value string="text7" />
    </item>
  </serverVariables>
</error>');

GO 100000

DECLARE @d DATETIME=GETDATE()
SELECT #testTbl.*
FROM #testTbl
CROSS APPLY XmlColumn.nodes('/error/serverVariables/item[@name="name5" and value/@string="My test 600"]') AS a(b);
SELECT CAST(GETDATE()-@d AS TIME) AS NodesFullPath_no_index;
GO

DECLARE @d DATETIME=GETDATE();
SELECT * 
FROM #testTbl
--WHERE XmlColumn.exist('//item[@name[. = "name5"] and value/@string[. = "My test 600"]]') = 1
--The same, just a bit shorter...
WHERE XmlColumn.exist('/error/serverVariables/item[@name="name5" and value/@string="My test 600"]') = 1;
SELECT CAST(GETDATE()-@d AS TIME) AS ExistFullPath_no_index;
GO

DECLARE @d DATETIME=GETDATE();
SELECT * 
FROM #testTbl
--WHERE XmlColumn.exist('//item[@name[. = "name5"] and value/@string[. = "My test 600"]]') = 1
--The same, just a bit shorter...
WHERE XmlColumn.exist('//item[@name="name5" and value/@string="My test 500"]') = 1;
SELECT CAST(GETDATE()-@d AS TIME) AS ExistShortPath_no_index;
GO

DECLARE @d DATETIME=GETDATE()
SELECT #testTbl.*
FROM #testTbl
CROSS APPLY XmlColumn.nodes('//item[@name="name5" and value/@string="My test 500"]') AS a(b);
SELECT CAST(GETDATE()-@d AS TIME) AS NodesShortPath_no_index;
GO

CREATE PRIMARY XML INDEX PXML_test_XmlColum1 ON #testTbl(XmlColumn);
CREATE XML INDEX IXML_test_XmlColumn2 ON #testTbl(XmlColumn) USING XML INDEX PXML_test_XmlColum1 FOR PATH;
GO

DECLARE @d DATETIME=GETDATE()
SELECT #testTbl.*
FROM #testTbl
CROSS APPLY XmlColumn.nodes('/error/serverVariables/item[@name="name5" and value/@string="My test 600"]') AS a(b);
SELECT CAST(GETDATE()-@d AS TIME) AS NodesFullPath_with_index;
GO

DECLARE @d DATETIME=GETDATE();
SELECT * 
FROM #testTbl
--WHERE XmlColumn.exist('//item[@name[. = "name5"] and value/@string[. = "My test 600"]]') = 1
--The same, just a bit shorter...
WHERE XmlColumn.exist('/error/serverVariables/item[@name="name5" and value/@string="My test 600"]') = 1;
SELECT CAST(GETDATE()-@d AS TIME) AS ExistFullPath_with_index;
GO

DECLARE @d DATETIME=GETDATE();
SELECT * 
FROM #testTbl
--WHERE XmlColumn.exist('//item[@name[. = "name5"] and value/@string[. = "My test 600"]]') = 1
--The same, just a bit shorter...
WHERE XmlColumn.exist('//item[@name="name5" and value/@string="My test 500"]') = 1;
SELECT CAST(GETDATE()-@d AS TIME) AS ExistShortPath_with_index;
GO

DECLARE @d DATETIME=GETDATE()
SELECT #testTbl.*
FROM #testTbl
CROSS APPLY XmlColumn.nodes('//item[@name="name5" and value/@string="My test 500"]') AS a(b);
SELECT CAST(GETDATE()-@d AS TIME) AS NodesShortPath_with_index;
GO

DROP TABLE #testTbl;