SQL - Define/Modify XML with variables - sql

Question

I'm trying to define an XML variable with VARCHAR characters inside of it...
Example
DECLARE #number nvarchar(10);
SET #number = '10'
DECLARE #xml XML;
SET #xml =
'
<Root>
<Node> Hello {sql:variable("#number")} </Node>
</Root>
'
However, the problem is that you can only set xml variables to string literals. Is there any way of doing this? Thanks!

Answer 1

Not sure why you want to do this. Use + to concatenate the variable inside the string then assign it to xml varibale
DECLARE #number NVARCHAR(10);
SET #number = '10'
DECLARE #xml XML;
SET #xml = '
<Root>
<Node> Hello ' + Isnull(#number,'') + ' </Node>
</Root>
'
To view the xml
select #xml
Result :
<Root>
<Node> Hello 10 </Node>
</Root>

Answer 2

DECLARE #number nvarchar(10) = '10';
DECLARE #xml XML = N'';
SELECT #xml = #xml.query('
<Root>
<Node>Hello {sql:variable("#number")}</Node>
</Root>
');
SELECT #xml;
/*
<Root>
<Node>Hello 10</Node>
</Root>
*/

Answer 3

In my eyes the existing answers (upvoted and accepted) are no good paths to go. One should (almost) never create XML via string concatenation...
Why not the simple way? Let the XML-engine do the hard work!
DECLARE #number nvarchar(10);
SET #number = '10'
DECLARE #xml XML=(SELECT 'Hello ' + #number FOR XML PATH('Node'),ROOT('Root'),TYPE);
SELECT #xml;
Returns
<Root>
<Node>Hello 10</Node>
</Root>
Just imagine, your (string!) variable includes some text with forbidden characters (><& or qoutes or one of the many special / far east / whatever characters)... Using FOR XML ... will implicitly do all the escaping for you...
One side effect: If your variable is NULL you will not get a NULL for all, but a valid XML with an empty node:
<Root>
<Node />
</Root>