Assumption here is that we're all on SQL2017+ for this to even work. But yeah, took them long enough to add this doozy to the built-in methods.

I like this, especially after having just got to grips with a MERGE and realised a few limitations myself (for example if you're logging row counts, there's no easy way...

Nevermind, I've just googled STRING_AGG and it's only available from SQL2017+

Is this related to a specific version of SQL Server?

I've just run it on SQL 2016 and the STRING_AGG method is unknown.