title: Date range in WHERE clause from 90 days ago to today's date
body: <p>I have written the following query, but in the WHERE clause I have used specific dates for the date range. I want the date range to be calculated automatically--that is, a period of 90 days up to today's date. How can I do it?</p>
  
  <pre><code>SELECT Orders.Day, 
  Orders.Month,
  Orders.Year, 
  Orders.Orders_Count,Orders.PaymentAmount, 
  Orders.Total_Payment_Authorized,
  Orders.ShipCity,   
  Orders.Total_Payment_Received, 
  Orders.SalesTax1, 
  Orders.SalesTax2, 
  Orders.SalesTax3, 
  Orders.TotalShippingCost, 
  Orders.OrderDetails_Count,   
  Orders.Quantity,
  Orders.COGS, 
  Orders.Profit,
  Orders.ProfitMargin  
  FROM (SELECT Orders.Day,Orders.Month,Orders.Year,Orders.Orders_Count,  Orders.PaymentAmount,Orders.Total_Payment_Authorized,Orders.ShipCity,Orders.Total_Payment_Received,Orders.SalesTax1,Orders.SalesTax2,Orders.SalesTax3,  Orders.TotalShippingCost,OrderDetails.OrderDetails_Count, OrderDetails.Quantity,OrderDetails.COGS,OrderDetails.Profit,OrderDetails.ProfitMargin   
  FROM (SELECT DATEPART(DD, Orders.OrderDate) AS Day, DATEPART(MM, Orders.OrderDate) AS Month,DATEPART(YY, Orders.OrderDate) AS Year,    Max(Orders.OrderDate) As OrderDate ,Max(Orders.ShipDate) As ShipDate, Count(Orders.OrderID) As Orders_Count, Sum(Orders.PaymentAmount) AS PaymentAmount, Sum(Orders.Total_Payment_Authorized) AS Total_Payment_Authorized,Orders.ShipCity AS ShipCity,   
  Sum(Orders.Total_Payment_Received) AS Total_Payment_Received, Sum(Orders.SalesTax1) AS SalesTax1,Sum(Orders.SalesTax2) AS SalesTax2 ,  Sum(Orders.SalesTax3) AS SalesTax3, Sum(Orders.TotalShippingCost) AS TotalShippingCost 
  FROM (((Orders WITH(NOLOCK) LEFT JOIN PaymentMethods    WITH(NOLOCK) ON Orders.PaymentMethodID = PaymentMethods.PaymentMethodID) 
  LEFT JOIN ShippingMethods WITH(NOLOCK) ON    Orders.ShippingMethodID = ShippingMethods.ShippingMethodID) 
  LEFT JOIN Customers WITH(NOLOCK) ON Orders.CustomerID = Customers.CustomerID)     
  WHERE Orders.OrderStatus &lt;&gt; 'Cancelled' GROUP BY Orders.ShipCity, DATEPART(DD, Orders.OrderDate),DATEPART(MM, Orders.OrderDate),DATEPART(YY, Orders.OrderDate))  Orders   
  INNER JOIN (SELECT DATEPART(DD, Orders.OrderDate) AS Day,DATEPART(MM, Orders.OrderDate) AS Month,DATEPART(YY, Orders.OrderDate) AS Year,  Count(OrderDetails.OrderDetailID) As OrderDetails_Count,
  Sum(OrderDetails.Quantity) AS Quantity,  Sum(OrderDetails.Vendor_Price * OrderDetails.Quantity) AS COGS,
  Case When SUM(Vendor_Price) IS NULL Then null Else Sum((Case When OrderDetails.ProductCode like 'DSC-%' Then 
  OrderDetails.ProductPrice - ISNULL(OrderDetails.Vendor_Price,0)  
  Else OrderDetails.ProductPrice - OrderDetails.Vendor_Price End) * OrderDetails.Quantity) End AS Profit,     
  CASE SUM(OrderDetails.ProductPrice * OrderDetails.Quantity) WHEN 0 THEN 0      
  ELSE ROUND(((SUM(OrderDetails.ProductPrice * OrderDetails.Quantity) - SUM(OrderDetails.Vendor_Price * OrderDetails.Quantity)) / SUM(OrderDetails.ProductPrice * OrderDetails.Quantity)) * 100, 1)   END AS ProfitMargin       
  FROM (((Orders WITH(NOLOCK) LEFT JOIN PaymentMethods WITH(NOLOCK) ON Orders.PaymentMethodID = PaymentMethods.PaymentMethodID)       
  LEFT JOIN ShippingMethods WITH(NOLOCK) ON Orders.ShippingMethodID = ShippingMethods.ShippingMethodID) LEFT JOIN Customers       
  WITH(NOLOCK)  ON Orders.CustomerID = Customers.CustomerID) LEFT JOIN OrderDetails WITH(NOLOCK) ON Orders.OrderID = OrderDetails.OrderID     
  WHERE Orders.OrderStatus &lt;&gt; 'Cancelled' AND DATEDIFF(dd, Orders.OrderDate, '03/01/2012') &lt;= 0 AND DATEDIFF(dd, Orders.OrderDate, '06/30/2012') &gt;= 0 AND Orders.ShipPostalCode IN ('96704','96710','96718','96719','96720','96721','96725','96726','96727','96728','96737','96738','96739','96740','96743','96745','96749','96750','96755','96760','96764','96771','96772','96773','96774','96776','96777','96778','96780','96781','96783','96785') 
  GROUP BY Orders.ShipCity, DATEPART(DD, Orders.OrderDate),DATEPART(MM, Orders.OrderDate), DATEPART(YY, Orders.OrderDate)) OrderDetails ON    Orders.Day = OrderDetails.Day AND Orders.Month = OrderDetails.Month AND  Orders.Year = OrderDetails.Year) Orders 
  ORDER BY Orders.Day DESC,   Orders.Month DESC,Orders.Year DESC
  </code></pre>