SELECT TimeSheets.EmployeeID, Month(WorkDate) as MonthPay , YEAR(WorkDate) AS YearPay,
   SUM(TimeSheets.HoursWorked * A.HourlyRate)  AS LaborDollars
        FROM TimeSheets
              	INNER JOIN WorkerRates A ON A.EmployeeID = TimeSheets.EmployeeID AND A.RateEffectiveDate <= WorkDate 
			AND A.RateAddedDate <= WorkDate
		LEFT JOIN WorkerRates B ON B.EmployeeID = TimeSheets.EmployeeID AND B.RateEffectiveDate <= WorkDate 
			AND B.RateAddedDate <= WorkDate AND A.RateEffectiveDate < B.RateEffectiveDate
	WHERE B.EmployeeID IS NULL
    GROUP BY TimeSheets.EmployeeID, Month(WorkDate),YEAR(WorkDate)