You can do it using WITH, as Marián suggested. Eg, for your example, I think this could work:
WITH maxOrderTime (orderId, “timestamp”) AS
SELECT orderId, max(“timestamp”) FROM order
WHERE “timestamp” < TIMESTAMPADD(DAY, -2, CURRENT_TIMESTAMP)
AND status = “Initiated”
GROUP BY orderId
SELECT order.orderId, order.qty, order.paymentId FROM order
ON order.orderId = maxOrderTime.orderId
AND order.“timestamp” = maxOrderTime.“timestamp”
I haven’t tried it, and I’m guessing a bit based on what you wrote. I don’t know how well it will perform.
Also, if you have more than 100k results in the end, you might get a “ran out of resources” (for a subquery) error, iirc.
But, worth a try!
I also note that this might be simpler in a native druid query, if you’re good with those, where you could use aggregators
like stringLast, floatLast, or doubleLast.
Hope that helps!