ABSTRACT
Data warehousing is one of the key data management technologies to support data mining and other decision support functions. Several organizations are building their own warehouses. Commercial database system vendors are marketing warehousing products. As stated in Chapter 2, the idea behind a data warehouse is that it is often cumbersome to access data from the heterogeneous databases. Several processing modules need to cooperate with each other to process a query in a heterogeneous environment. Therefore, a data warehouse will bring together the essential data from the heterogeneous databases. This way the users need to query only the warehouse. Essentially data warehouses provide support for decision support of an enterprise. For example, although the data sources may have the raw data, the data warehouse may have correlated data, summary reports, and aggregate functions applied to the raw data.
