Data Warehousing

A data warehouse is a collection and summarization of information from multiple databases and database tables. The primary purpose of a data warehouse is not data storage, but the collection of information for decision-making. Typically, a data warehouse extracts updated information from operational databases on a regular basis (nightly, hourly, etc.). This forms a snapshot of collected data that can be organized into a logical structure based on your analytical needs.

Data warehouses allow you to express your information needs logically, without being constrained to database fields and records. Using the correct data mining tools, it is possible to display information from a data warehouse in ways that are not possible using SQL or other basic query languages. Unlike a relational database, a data warehouse can present information in multidimensional format. This representation is called a hypercube, and contains layers of rows and columns. Using this model a company could, for instance, track sales of multiple products in multiple regions over a given period of time, all in the same view.

A data warehouse can contain extremely large amounts of information, and many users will only need to access a portion of this. Information in a data warehouse can be organized into data marts, which are subsets of data with a specific focus. Data marts can provide an analyst with a more efficient set of working data relevant to, for instance, a specific business process or unit of the company.