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Definition: Extraction, Transformation and Loading (ETL)
Extraction, Transformation and Loading are a set of processes going on at the backstage of a data warehouse. ETL is generally used in the migration of data from one database to another or to convert databases from one format to another. It is also used to form data marts and data warehouses (Storage areas for data). 3 stages in ETL are:
Extraction – Identification and extraction of desired data from database systems and applications. It involves consolidation of data from different sources. Parsing the data may be essential to check if it matches a required pattern.
Transformation – The data extracted from the source may require transformation before loading into the end target. The transformation is carried out by applying rules, using lookup tables or combining the data with other data.
Loading – This process loads the data into the end target or database. It may or may not involve overwriting the existing information.