How to get value of a node with namespace prefix [duplicate] - sql

Question

This question already has answers here:
sql server parse xml with namespace
(2 answers)
Closed 11 months ago.
So, I have got the following query that I tried to get the value between the nodes:
<oas:Base64Assertion>235fkl53</oas:Base64Assertion>
I want to extract the value 235fkl53. I tried with the following query:
declare #x xml = '
<soapenv:Header>
<oas:Security>
<oas:Base64Assertion>
<oas:Security xmlns:oas="http://example.com">
<oas:Base64Assertion>235fkl53</oas:Base64Assertion>
</oas:Security>
</oas:Base64Assertion>
</oas:Security>
</soapenv:Header>
';
select cast(#x.value('(//oas:Base64Assertion)[1]', 'nvarchar(max)') as xml).query('//value/text()') as cdata;
But I get the following error:
Msg 2229, Level 16, State 1, Line 13 XQuery [value()]: The name "oas"
does not denote a namespace.
Any tips on how to achieve this?

Answer 1

You did not add the namespaces in the XML you posted so I have added them in the following example based on where I think they should be.
You need to add WITH NAMESPACE before using namespace prefixes in XQueries:
declare #x xml = '<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope" xmlns:oas="http://example.com">
<soapenv:Header>
<oas:Security>
<oas:Base64Assertion>
<oas:Security>
<oas:Base64Assertion>235fkl53</oas:Base64Assertion>
</oas:Security>
</oas:Base64Assertion>
</oas:Security>
</soapenv:Header>
</soapenv:Envelope>
';
WITH XMLNAMESPACES ('http://example.com' AS oas)
SELECT #x.value('(//oas:Base64Assertion)[1]', 'nvarchar(max)');
SELECT #x.value('declare namespace oas="http://example.com"; (//oas:Base64Assertion)[1]', 'nvarchar(max)');
DB<>Fiddle