The power of Cross (Cartesian) Joins

This is a very good example of where the Cartesian (Cross) Join may be very helpful. Though proper understanding and enough experimentation should be done to try it out.
Jeff @ SQLTeam.com

It explains an example where a Join may be required to return some value ['0'] in this case when there are no matching records found. for e.g. return 0 for sales of all combination of products and stores which dont have a value i.e. null.


SELECT S.Store, P.Product, ISNULL(C.TotalSales,0) as TotalSales
FROM Stores S
CROSS JOIN Products P
LEFT OUTER JOIN
(SELECT Store, Product, SUM(Sales) as TotalSales
FROM Sales
GROUP BY Store, Product) C
ON
S.Store = C.Store AND
P.Product = C.Product

Also Refer:
Join Clause in SQl