I have a requirement that :
Among devices that were not operational this month ,how many were operational last month and how many were operational 2 months back.
Ex-
March month-Total Devices-100
Operational Devices-60
Non-Operational Devices-100-60=40
Now,
Among these 40 devices(Non operational in March month), How many device were operational in Feb month?
How many devices were operational in Jan month?
My question is: How to restrict calculation of jan month and feb month device count among these 40 devices only?
