Excellent question. I learned something useful.

One application of OVER that seems to have potential (note hedging 😉 ) is that it allows applying aggregate function to more than one different grouping in the same query. For instance,

select customerID, productID, orderDate, orderAmount,

CustomerTotal = sum(orderAmount) over (partition by customerID),

ProductTotal = sum(orderAmount) over (partition by productID)

from Orders

Any thoughts on performance?

Edited for clarity.