我正在尝试编写一个XPath查询来提取将始终使用相同缩写的特定命名空间的URI。
示例：
<RequestPacket xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:a="urn:dont:really:care">
<a:Requests xmlns:queryNS="urn:uri:i:need">
<a:Request xsi:type="queryNS:GetImportantData">
<queryNS:Version>3</queryNS:Version>
...
</a:Request>
</a:Requests>
</RequestPacket>
我需要提取与queryNS命名空间相对应的URI，在我的示例中为urn:uri:i:need。
这可能吗？如果是这样，有人可以帮忙吗？
我试图使用namespace-uri()函数来获取它，但为了这样做，我必须指定一个节点，我只能通过在每个节点指定命名空间来做（这就是我所做的）试图搞清楚）。所以它看起来像鸡和鸡蛋的情况。
谢谢！
答案 0 :(得分：3)
有两种方法：
DECLARE @xml XML=
N'<RequestPacket xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:a="urn:dont:really:care">
<a:Requests xmlns:queryNS="urn:uri:i:need">
<a:Request xsi:type="queryNS:GetImportantData">
<queryNS:Version>3</queryNS:Version>
...
</a:Request>
</a:Requests>
</RequestPacket>';
- 对一个节点使用namespace-uri()，该节点
SELECT @xml.value(N'namespace-uri((//*:Version)[1])',N'nvarchar(max)')
- 这可能是罕见的情况之一，FROM OPENXML is still helpful。试试这个：
DECLARE @docHandle INT
EXEC sp_xml_preparedocument @docHandle OUTPUT, @xml;
SELECT * FROM OPENXML (@docHandle, '',1)
EXEC sp_xml_removedocument @docHandle
结果
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| id | parentid | nodetype | localname | prefix | namespaceuri | datatype | prev | text |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 0 | NULL | 1 | RequestPacket | NULL | NULL | NULL | NULL | NULL |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 2 | 0 | 2 | xsi | xmlns | NULL | NULL | NULL | NULL |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 10 | 2 | 3 | #text | NULL | NULL | NULL | NULL | http://www.w3.org/2001/XMLSchema-instance |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 3 | 0 | 2 | a | xmlns | NULL | NULL | NULL | NULL |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 11 | 3 | 3 | #text | NULL | NULL | NULL | NULL | urn:dont:really:care |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 4 | 0 | 1 | Requests | a | urn:dont:really:care | NULL | NULL | NULL |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 5 | 4 | 2 | queryNS | xmlns | NULL | NULL | NULL | NULL |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 12 | 5 | 3 | #text | NULL | NULL | NULL | NULL | urn:uri:i:need |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 6 | 4 | 1 | Request | a | urn:dont:really:care | NULL | NULL | NULL |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 7 | 6 | 2 | type | xsi | http://www.w3.org/2001/XMLSchema-instance | NULL | NULL | NULL |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 13 | 7 | 3 | #text | NULL | NULL | NULL | NULL | queryNS:GetImportantData |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 8 | 6 | 1 | Version | queryNS | urn:uri:i:need | NULL | NULL | NULL |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 14 | 8 | 3 | #text | NULL | NULL | NULL | NULL | 3 |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
| 9 | 6 | 3 | #text | NULL | NULL | NULL | 8 | ... |
+----+----------+----------+---------------+---------+-------------------------------------------+----------+------+-------------------------------------------+
您可以使用parentid和nodetype来查找您的URI：属性queryNS的ID为5。这是元素12的parentid，其中#text是您要查找的URI。但是这不能在 adhoc / inline 查询中使用。
.query() SELECT @xml.query(
N'
<root>
{
for $nd in //*
return
<nd ns="{namespace-uri($nd)}" name="{local-name($nd)}" value="{($nd/text())[1]}">
{
for $attr in $nd/@*
return
<attr ns="{namespace-uri($attr)}" name="{local-name($attr)}" value="{$attr}" />
}
</nd>
}
</root>
');
结果
<root>
<nd ns="" name="RequestPacket" value="" />
<nd ns="urn:dont:really:care" name="Requests" value="" />
<nd ns="urn:dont:really:care" name="Request" value="
 ...
 ">
<attr ns="http://www.w3.org/2001/XMLSchema-instance" name="type" value="queryNS:GetImportantData" />
</nd>
<nd ns="urn:uri:i:need" name="Version" value="3" />
</root>
答案 1 :(得分：1)
只需使用命名空间轴：
string(namespace::queryNS)
或者如果名称空间前缀不是静态已知的
string(namespace::*[name()=$prefix])
命名空间轴在XQuery中不可用，并且在XPath 2.0+中已弃用，因此您可以改为使用
namespace-uri-for-prefix($prefix, $element)
CAVEAT ：我刚刚注意到这个问题被标记为sql-server。我对SQL Server中的XPath / XQuery实现一无所知，除了它并不总是符合这一点。