SQL-SERVER Select UPDATE OUTPUT as XML - sql-server

Question

Running on SQL Server 2016.
I have a routine that updates information across servers. I want to hold a list of any changes that I have been required to make. I am trying to output the changed columns as XML for basic storage, and would like to do this directly from the OUTPUT generated by the insert/update/delete if possible.
As an example:
DROP TABLE IF EXISTS Test
CREATE TABLE Test (myKey INT, myValue INT)
INSERT INTO dbo.Test (myKey, myValue)
VALUES (1, 1), (2, 2), (3, 3)
UPDATE dbo.Test
SET myValue = myValue + 10
OUTPUT Deleted.*
, Inserted.*
WHERE myKey < 3
SELECT *
FROM dbo.Test
FOR XML AUTO
DROP TABLE dbo.Test
I know I can set up a TVP to receive the output and then convert to XML from there, but it seems like I'm taking extra steps to do something that should be quite straight forward.
DROP TABLE IF EXISTS Test
CREATE TABLE Test (myKey INT, myValue INT)
INSERT INTO dbo.Test (myKey, myValue)
VALUES (1, 1), (2, 2), (3, 3)
DECLARE #OutputValues AS TABLE(dMyKey INT, dMyValue INT, iMyKey INT, iMyValue INT)
UPDATE dbo.Test
SET myValue = myValue + 10
OUTPUT Deleted.myKey
, Deleted.myValue
, Inserted.myKey
, Inserted.myValue
INTO #OutputValues
WHERE myKey < 3
SELECT *
FROM #OutputValues
FOR XML AUTO
DROP TABLE dbo.Test
While this second piece of code does achieve the sort of output I am looking for, going via a TVP seems to be a bit wasteful.
If I can format the output from the original code directly as XML I feel that would be a better solution. However, I can't see any way of doing so.
Many Thanks.

Answer 1

What are you trying to achieve? Such monitoring / auditing tasks are most likely better solved within a trigger...
The output clause does not allow sub-selects... The only way - not generic and rather ugly - which came into my mind was this (the clue is the implicit cast from nvarchar to xml):
CREATE TABLE Test (myKey INT, myValue INT)
INSERT INTO dbo.Test (myKey, myValue)
VALUES (1, 1), (2, 2), (3, 3)
DECLARE #OutputValues AS TABLE(dMyKey INT, dMyValue INT, iMyKey INT, iMyValue INT,Changed XML)
UPDATE dbo.Test
SET myValue = myValue + 10
OUTPUT Deleted.myKey
, Deleted.myValue
, Inserted.myKey
, Inserted.myValue
, N'<root><deletedKey>' + CAST(deleted.myKey AS NVARCHAR(MAX)) + N'</deletedKey>' +
N'<deletedValue>' + CAST(deleted.myValue AS NVARCHAR(MAX)) + N'</deletedValue>' +
N'<insertedKey>' + CAST(inserted.myValue AS NVARCHAR(MAX)) + N'</insertedKey>' +
N'<insertedValue>' + CAST(inserted.myValue AS NVARCHAR(MAX)) + N'</insertedValue>' +
N'</root>'
INTO #OutputValues
WHERE myKey < 3
SELECT Changed
FROM #OutputValues
DROP TABLE dbo.Test
attention: If your values include forbidden characters (such as <, > or &) this will fail!