SQL Server 2008 trigger to modify file - file

Question

I need help please about SQL Server 2008 and triggers.
The context: a machine has generated data (number: integer) that I need to inject into a xml file. This data changes a few times a day, but I need it in real time.
Problem: the data is not available directly from the machine, no way... but this machine feeds a SQL Server 2008 database.
So, I think a better way is using a SQL Server trigger. Am I wrong ?
Here's code I'm using:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER TRIGGER [dbo].[Test]
ON [dbo].[Table_machine]
AFTER UPDATE
AS
IF UPDATE(Valeur)
BEGIN
**********************************
END
This trigger works on 'Valeur' update but I don't know how to modify my xml file?

Answer 1

I would strongly recommend AGAINST putting such logic that does a lot of conversion and writes out to a file system into a trigger - it will slow down the normal operation of the database quite significantly. And triggers and T-SQL are severely limited in what they can do in the file system.
My approach would be:
create a separate application/tool, e.g. in C# or whatever other language you know, and handle the logic of creating that XML from the database and storing it into a file in there
have that tool scheduled by e.g. Windows Scheduler or some other mechanism to be run on a regular basis - whether that's every 10 minutes, or every hour is up to you to decide
The main benefits are:
you've not severely slowed down your database operation
you have more programming power at your disposal to write that logic
you can schedule it to run as frequently or as infrequently as needed (e.g. every 5 minutes during working weekdays from 6am to 10pm - and only once an hour outside these hours - or whatever you choose to do)

Answer 2

Thanks for reply !
It's a good idea and I will try this solution to compare difference with my new solution.
I've tried with trigger EXEC xp_cmdshell 'D:\MyApp.exe'
I create MyApp.exe application who do all modifications in my xml file.
It works perfectly except to send modified data in sql database. I don't know how to take this value...
It must be EXEC xp_cmdshell 'D:\MyApp.exe Valeur' but I don't know how to grab 'Valeur'.
With this solution, database must NOT be too slow, no ? Because Trigger only launch a shell command ?
The only one value I need in database could change 20 times per minute or only 2 times per day but I need this value in 'real time'. So scheduler would not be accurate enough...