Database Reference
In-Depth Information
Figure 24-5.
Data Warehouse with Staging Area and Data Marts
24.5 Extraction, Transformation, and Loading
The data warehouse must be loaded regularly so that it can serve its purpose of
facilitating business analysis. To do this, data from one or more operational databases
needs to be extracted, transformed (where necessary), and copied into the warehouse.
The acronym ETL is often used to refer to this extraction, transformation and loading
of data. The acronym is perhaps too simplistic, since it omits the transportation phase
and implies that each of the other phases of the process is distinct. We refer to the entire
process, including data loading, as ETL. However, you should understand that ETL refers
to a broad process, and not three well-defined steps.
The methodologies and tasks of ETL have been well known for many years, and are
not necessarily unique to data warehouse environments. A wide variety of proprietary
applications and database systems are used as the IT backbone business enterprises.
