Converting XML node values to comma separated values in SQL - sql

Question

I am trying to convert XML node values to comma separated values but, getting a
Incorrect syntax near the keyword 'SELECT'.
error message
declare #dataCodes XML = '<Root>
<List Value="120" />
<List Value="110" />
</Root>';
DECLARE #ConcatString VARCHAR(MAX)
SELECT #ConcatString = COALESCE(#ConcatString + ', ', '') + Code FROM (SELECT T.Item.value('#Value[1]','VARCHAR(MAX)') as Code FROM #dataCodes.nodes('/Root/List') AS T(Item))
SELECT #ConcatString AS Result
GO
I tried to follow an article but not sure how to proceed further. Any suggestion is appreciated.
Expectation:
Comma separated values ('120,110') stored in a variable.

Answer 1

Try this;
DECLARE #dataCodes XML = '<Root>
<List Value="120" />
<List Value="110" />
</Root>';
DECLARE #ConcatString VARCHAR(MAX)
SELECT #ConcatString = COALESCE(#ConcatString + ', ', '') + Code
FROM (
SELECT T.Item.value('#Value[1]', 'VARCHAR(MAX)') AS Code
FROM #dataCodes.nodes('/Root/List') AS T(Item)
) as TBL
SELECT #ConcatString AS Result
GO
You just need to add an alias to your sub SQL query.

Answer 2

For future readers, XML data can be extracted into arrays, lists, vectors, and variables for output in comma separated values more fluidly using general purpose languages. Below are open-source solutions using OP's needs taking advantage of XPath.
Python
import lxml.etree as ET
xml = '<Root>\
<List Value="120" />\
<List Value="110" />\
</Root>'
dom = ET.fromstring(xml)
nodes = dom.xpath('//List/#Value')
data = [] # LIST
for elem in nodes:
data.append(elem)
print((", ").join(data))
120, 110
PHP
$xml = '<Root>
<List Value="120" />
<List Value="110" />
</Root>';
$dom = simplexml_load_string($xml);
$node = $dom->xpath('//List/#Value');
$data = []; # Array
foreach ($node as $n){
$data[] = $n;
}
echo implode(", ", $data);
120, 110
R
library(XML)
xml = '<Root>
<List Value="120" />
<List Value="110" />
</Root>'
doc<-xmlInternalTreeParse(xml)
data <- xpathSApply(doc, "//List", xmlGetAttr, 'Value') # LIST
print(paste(data, collapse = ', '))
120, 110

Answer 3

To do this without a variable, you can use the nodes method to convert the xml nodes into a table format with leading commas, then use FOR XML PATH('') to collapse it into a single line of XML, then wrap that in STUFF to convert it to varchar and strip off the initial leading comma:
DECLARE #dataCodes XML = '<Root>
<List Value="120" />
<List Value="110" />
</Root>';
SELECT STUFF(
(
SELECT ', ' + T.Item.value('#Value[1]', 'VARCHAR(MAX)')
FROM #dataCodes.nodes('/Root/List') AS T(Item)
FOR XML PATH('')
), 1, 2, '')