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What is ETL and how is it different from ELT?
ETL means extract, transform, then load: data is cleaned and reshaped before it reaches the warehouse. ELT means extract, load, then transform: raw data lands in the warehouse first and is transformed there using SQL. Modern cloud warehouses make ELT the common choice because storage is cheap and transformations are easier to version and rerun.
With ETL, the transformation happens in a separate tool or script, so the warehouse only holds finished data. If the logic is wrong, you may need to re-extract from the source.
With ELT, the raw copy is kept, so you can change your logic and rebuild without calling the source system again. Tools such as dbt handle the transform step in SQL.
For small and mid-sized companies, ELT is usually simpler to maintain, but ETL can still make sense when you must remove sensitive fields before data leaves a source system.
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