filter

or a query of a query result.

If you had select * from CustomerOrders where ordercount > 0 going into an Excel spread sheet you could then provide the ability to filter that result say for ordercount between 10 and 15.

The important thing to bear in mind is if teh CustomerOrders table is changed this will not be visible, you have to re-execute the underlying select statement to get that.

The boon is you can apply filters at will without making a round trip back to the actual source.

So it's used for whatever you want.