After reading the excellent Web-exclusive article “Calculating Row Numbers in SQL Server 2005,” April 2004, InstantDoc ID 42302, I started doing some tests and found one case in which I couldn’t think a way to use the ROW_NUMBER() function without using subqueries. Using the Northwind database, I wanted to write a query to create a new identifier for each order and another new identifier for each product that belongs to an order. The result should be similar to
\[Order Details\] in Northwind Expected Query Output 10248 11 14.0000 12 1 1 14.0000 12 10248 42 9.8000 10 1 2 9.8000 10 10248 72 34.8000 5 1 3 34.8000 5 10249 14 18.6000 9 2 1 18.6000 9 10249 51 42.4000 40 2 2 42.4000 40 10250 41 7.7000 10 3 1 7.7000 10 10250 51 42.4000 35 3 2 42.4000 35 10250 65 16.8000 15 3 3 16.8000 15
Without the ROW_NUMBER() function, I could get the expected result with this query:
SELECT (SELECT count(*) FROM orders as o2 WHERE o2.OrderID FROM Orders AS O inner join \[order details\] AS OD ON O.OrderID = od.OrderID inner join \[products\] as p on p.productID = od.productiD
With the ROW_NUMBER() function, I found the result with this query:
SELECT NewOrderNumber, ROW_NUMBER() OVER (PARTITION BY O.ORDERID ORDER BY OD.ProductID) as ProductNumber, OD.OrderID, OrderDate, OD.ProductId, ProductName, Quantity FROM (SELECT ROW_Number() OVER (ORDER BY OrderID) as NewOrderNumber, * FROM Orders) AS O INNER JOIN \[Order Details\] AS OD ON O.OrderID = OD.oRDERid inner join \[Products\] as p ON p.productID = od.productiD
However, I couldn’t think of a way to resolve this query without using subqueries. I was out of ideas, so I asked Itzik Ben-Gan, who wrote “Calculating Row Numbers in SQL Server 2005.” Because the order IDs aren’t unique in the result of the join, he suggested that I simply use the DENSE_RANK() function instead of the ROW_NUMBER() function:
SELECT DENSE_RANK() OVER(ORDER BY O.OrderID) as NewOrderNumber, ROW_NUMBER() OVER(PARTITION BY OD.OrderID ORDER BY OD.ProductID) as ProductNumber, OD.OrderID, OrderDate, OD.ProductId, ProductName, Quantity FROM Orders AS O JOIN \[Order Details\] AS OD ON O.OrderID = OD.OrderID JOIN \[Products\] AS P ON P.ProductID = OD.ProductID
This query produced the expected output.
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