ETL is an abbreviation for extraction, transformation and loading of data, and denotes the process by which data gets from source systems into a target store in a usable form. Extraction means obtaining data from an interface, database or file; transformation means cleaning it, unifying formats, recalculating and supplementing it; loading means writing it to the target. A common variant is the order in which data is first loaded and only transformed in the target. For a company, it is essential that this flow be repeatable, scheduled and monitored, without an alert on failure, reports look correct even though they contain old figures. The design should therefore include error handling, the ability to rerun without duplicates, and a record of when the data last passed through.
See also: Data Warehouse, Data quality in analytics, Record deduplication.
