How to rotate SQL Table

There was very good customer from Australia. He always had interesting projects. One of this project was to show report on products sales. At start it looks like simple project, but there were two issues:
1) Customer had very big amounts of data in MS SQL.
2) He would like to show data grouped in columns, not rows.

First version of project does grouping in the columns at the C# code, but with such big amount of data it was crazy slow and takes a lot of memory. This is why grouping has been moved to the MS SQL side. Here is a beautiful script (sorry, but can't remember original source):

Let me introduce myself

My name is Sergey. I am developer from the prehistoric times. It starts a lot of years ago, when computers were big and slow and continues until today. For this long period i have got great experience: machine codes, Assembler, Basic, Fortran, C, Pascal, Prolog, later Delphi, VB, C++, C#, Java, PHP, Perl and sure databases DBase, Paradox, FoxPro, MSSQL, MySQL, PostGre...Really it should take a lot of time to describe everything.

Since 2002 i develop for Web. More then 75% of my projects are DotNetNuke oriented. DotNetNuke (DNN) is great Content Management System and this is good to work with this product and community. But DNN is not my single priority. Also a lot of requests from customers on synchronizing data between different products. There were some projects for NopCommerce, Magento, OpenErp, OpenBravo Pos.

This work is good. It allows me to work remotely with different customers from around the world. Thats great opportunity and very good experience!