ETL is the foundational data integration pattern that moves data from source systems to target destinations, transforming it along the way to meet analytical or operational requirements. It powers data warehouses, business intelligence, and analytics platforms across industries by ensuring clean, consistent, and queryable data. The key distinction: transformations happen before loading (unlike ELT, where transformations occur after loading into the destination). Understanding ETL patterns, from extraction strategies to slowly changing dimensions, is essential for building reliable, scalable, and performant data pipelines that teams trust.

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