This ‘process’ is often used in OLAP or analytical data system. Data from multiple sources is gathered (and thus extracted), transformed and then loaded into the database.
Sometimes, the transformation happens after the load, and are named ELTs.
Transformations are sometimes necessary to normalize the data or naming conventions.
Reference
Kleppmann, Martin, and Chris Riccomini. Designing Data-Intensive Applications: The Big Ideas behind Reliable, Scalable, and Maintainable Systems. Second Edition, O’Reilly Media, 2026.