The Operational data is the source for all business intelligence applications, but the data is typically not in the correct format to support the decision making process in a business. Also, nowadays, banks are storing more information than ever before. Decision makers must have the right information at the right time to help them make more informed and intelligent decisions. The data in the operational database represents current transactions, however the decisions are based on a different time frame; that is there is no time component. On the other hand, data in operational databases are stored with a functional or process orientation, what really decision-makers would like to have is subject orientation of data, which facilitates multiple views for data and decision making. Data Warehousing & Data Mining are the right solution that makes the above possible. One of the main goal of implementing a data warehouse is to turn the wealth of corporate data into information that can be used in the daily decision making process. In this paper, I highlighted the need of data warehousing for banks and provided an approach to build the warehouse suitable to banks.