Three Moons of Revenue Flow: Track Supplier Revenue Trends with a 3-Month Rolling Window

          with MonthlyRevenue as
  (select s.SupplierID,
          od.ProductID,
          DATE_TRUNC('month', o.OrderDate) as MonthStart,
          SUM(od.Quantity * od.UnitPrice * c.ExchangeRateToBase) as RevenueBase
   from Orders o
   join OrderDetails od on o.OrderID = od.OrderID
   join Currency c on od.CurrencyID = c.CurrencyID
   join Products p on od.ProductID = p.ProductID
   join Suppliers s on p.SupplierID = s.SupplierID
   where o.Status = 'Completed'
   group by s.SupplierID,
            od.ProductID,
            DATE_TRUNC('month', o.OrderDate))
select SupplierID,
       ProductID,
       MonthStart,
       SUM(RevenueBase) over (partition by SupplierID,
                                           ProductID
                              order by MonthStart rows between 2 PRECEDING and current row) as RollingRevenueBase
from MonthlyRevenue
order by SupplierID,
         ProductID,
         MonthStart;