The artificial key is the unique identifier that is used to join a dimension record to a fact table. When joining dimensions to fact tables it would be possible to perform the join using the business key. For fact tables with a large number of records this however would result in slow query times and very large indexes. As query time is one of our key drivers in data warehouse implementations the best answer is always to use some form of artificial key. A price is paid in the additional processing required to build the fact table rows, but this is offset by the reduced query times and index sizes. We can also make use of database specific features such as bitmap indexes in Oracle.

The artificial key is an integer and is built sequentially from 1 upwards. See the section on artificial keys for a more detailed explanation. An artificial key is sometimes referred to as a "surrogate" key.

Dimensions are often sourced from one table in the base application. In many cases there are also codes that require description lookups to complete the de-normalization of the dimensional data. The process for building a dimension is the same for most other tables and begins with the drag and drop of the load table that contains the bulk of the dimensional information.