You don't need to scan the table twice 😉
SELECT Id, layer,
SUM(CASE WHEN test > 1 THEN test * duration END) /
SUM(duration * 1.0)
FROM #test
GROUP BY ID,
layer
Luis C.
General Disclaimer:
Are you seriously taking the advice and code from someone from the internet without testing it? Do you at least understand it? Or can it easily kill your server?
How to post data/code on a forum to get the best help: Option 1 / Option 2