Some time we need to summarize data very quickly without writing very complex query. CUBE And ROLL UP are great commands that give us very good summary options.
We can summarize the data without writing dirty and complex queries with the help of CUBE and ROLL Up Operators.
I have found a great link for CUBE and ROLL UP to understand it deeply.Here is the link for that.
http://databases.about.com/od/sql/l/aacuberollup.htm