Get multiple xml nodes (delimited) - sql

Question

I have a table with a xml that is formatted something like this (simplified for readability)
<parentItem xmlns:i="http://tempuri.org/1" xmlns="http://tempuri.org/2">
<ItemA></ItemA>
<ItemB></ItemB>
<ItemC xmlns:d2p1="http://tempuri.org/3">
<d2p1:string>value1</d2p1:string>
<d2p1:string>value2</d2p1:string>
<d2p1:string>value3</d2p1:string>
<!-- .... (0 to many strings here) -->
</ItemC>
</parentItem>
The only think I care about are the values in parentItem > ItemC > string
I would like to get those values delimited by something, such as a comma
Desired Result: "value1,value2,value3"
currently I can get one value by doing this:
SELECT CAST([QueryXml] as xml).value('(/*:parentItem/*:ItemC/node())[1]','nvarchar(max)')
FROM [opendb].[dbo].[MyTable]
Result: "value1"
I can also get all the values like this:
SELECT CAST([QueryXml] as xml).value('(/*:ConflictsSearchTermQuery/*:TermItems)[1]','nvarchar(max)')
FROM [opendb].[dbo].[ConflictsSearchTerms]
Result: "value1value2value3"
but I'm looking to get a delimited set of values
Desired Result: "value1,value2,value3"

Answer 1

To get multiple values out of XML you need to use the nodes() method of the XML data type.
However, since this method does not return a single, scalar value (but a rowset), you need to call it through CROSS APPLY.
WITH MyTable AS (
SELECT 1 AS ID, CAST('<parentItem xmlns:i="http://tempuri.org/1" xmlns="http://tempuri.org/2">
<ItemA></ItemA>
<ItemB></ItemB>
<ItemC xmlns:d2p1="http://tempuri.org/3">
<d2p1:string>value1</d2p1:string>
<d2p1:string>value2</d2p1:string>
<d2p1:string>value3</d2p1:string>
<!-- .... (0 to many strings here) -->
</ItemC>
</parentItem>' AS XML) AS QueryXml
)
SELECT
t.ID,
x.node.value('.', 'varchar(100)') AS nodeValue
FROM
MyTable t
CROSS APPLY QueryXml.nodes('
declare namespace i="http://tempuri.org/1";
declare namespace def="http://tempuri.org/2";
declare namespace d2p1="http://tempuri.org/3";
/def:parentItem/def:ItemC/d2p1:string'
) x(node)
gives you
ID nodeValue
----------- ------------------
1 value1
1 value2
1 value3
After that, if you really must, standard techniques for concatenating values in SQL Server apply.
Note that I have properly declared the namespaces in the XQuery instead of using *. Namespaces are important, don't ignore them.