Question

Is it possible to use a nvarchar type sproc variable in an xquery insert statement within the stored procedure?
What I mean is something like this, in which an element is inserted only if a child element with the sought for value is present:

DECLARE @profiles_xml xml
DECLARE @profile_id int
DECLARE @user_id nvarchar(50)
SET @profile_id = 20
SET @user_id ='BC4A18CA-AFB5-4268-BDA9-C990DAFE7783'
SET @profiles_xml = (SELECT profiles from tbl_applied_profiles WHERE profiles.value('(Profile/ID)[1]','int')= @profile_id)
SET @profiles_xml.modify('
insert
if(/Profile/User/ID="user_id")
then <Activity>activity_name5</Activity>
else()
as first
into (/Profile/User/Activities)[1]')

The xml which @profiles_xml contains looks like this:

<Profile>
  <ID>20</ID>
  <User>
    <ID>BC4A18CA-AFB5-4268-BDA9-C990DAFE7783</ID>
    <Name>somename</Name>
    <Activities>
      <Activity>activity_name2</Activity>
    </Activities>
  </User>
</Profile>

Answer 1

You need to use sql:variable("@user_id"), i.e.

SET @profiles_xml.modify('
insert
if(/Profile/User/ID=sql:variable("@user_id"))
then <Activity>activity_name5</Activity>
else()
as first
into (/Profile/User/Activities)[1]');
select @profiles_xml;