Thank you very much. This was the problem. But two more questions: Why should NULL + Something be NULL instead of Something? Where is the setting for that?

Hmmm...

I indeed forgot about the trigger, which is keeping the history of all changes in another table...

But the problem seems to be here:

SET ...

Thanks for the code.

I tried your code with Output, but it didn't work. I tried with the Output after the SET, which brought the following message: The target table 'Unternehmen'...

Thank you for the fast reaction. Yes, I think you understood the problem I am trying to solve.

In my words:

There is a list of numbers KdNrVormerkung in the table LoeschvormerkungenK....

Thanks for your quick reply.

Since this is a shortened version of the trigger, the insert-statement is a lot longer and I have 10 different tables to write in. This makes...

SELECT ...+ ',' + ' '.... FOR XML PATH('')

did the trick. It seemed a lot more complicated on first sight.

Why should I use CROSS APPLY or STUFF in addition?...

Hmmm... CROSS APLLY looks promising as a solution for that problem.

But I hoped there would be...

Complete table definitions would include a lot of stuff, that is not needed here.

Let's keep it simple

We have one table Files, which has 2 fields we need here

-FileID

-EditedDate...