There r only 2 ways available to get data from a datawarehouse or a database.one is using sql statement and other method is using an OLAP tool(ex:cognos, business objects.....)So Hyperion is an example for a OLAP tool. ETL is a process of Extracting data from a source systems(a system where client's transactional business information resides) and performing business logic(applying TRANSFORMATION rules) on the collected source information(business logic depends on business requirements), and LOADING the precise data into a warehouse(propably a relational database). OLAP comes into picture after ETL developers design the warehouse........by using olap tools a business user can generate standard reports(without having sql knowledge he can do this) rest view on http://www.geekinterview.com/question_details/22108