SELECT FirstName + ' ' + LastName 'Imię i nazwisko', YEAR(OrderDate) Rok, MONTH(OrderDate) Miesiąc, COUNT(SalesOrderID) 'W miesiącu',
		SUM(COUNT(SalesOrderID)) OVER(PARTITION BY FirstName + ' ' + LastName, YEAR(OrderDate)) 'W roku',
		SUM(COUNT(SalesOrderID)) OVER(PARTITION BY FirstName + ' ' + LastName, YEAR(OrderDate) ORDER BY MONTH(OrderDate) ROWS BETWEEN
			UNBOUNDED PRECEDING AND CURRENT ROW) 'W roku narastająco',
		SUM(COUNT(SalesOrderID)) OVER(PARTITION BY FirstName + ' ' + LastName, YEAR(OrderDate) ORDER BY MONTH(OrderDate) ROWS BETWEEN
			1 PRECEDING AND CURRENT ROW) 'Obecny i poprzedni miesiąc'
FROM Sales.SalesOrderHeader header JOIN Person.Person pers ON header.CustomerID  = pers.BusinessEntityID
GROUP BY FirstName + ' ' + LastName, YEAR(OrderDate), MONTH(OrderDate)
ORDER BY FirstName + ' ' + LastName