All companies need information for taking decisions. Usually, there are many data propagated in the IT systems of a company, but transforming them into information which can be analyzed for decision taking is a heavy process. Data warehouse (DW) and business intelligence (BI) systems as well as decision support systems have the meaning of helping companies to answer in real time to complex questions. There are different techniques of data mining and choosing the corresponding tool lead to the way of finding relevant answers for a certain organization. The process is a dynamic one and these answers are changing in time accordingly to the business strategy of the organization.