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ETL and ELT

Updated Nov 30, 2021 ·

Overview​

ETL and ELT both deal with extracting, transforming, and loading data, but the order of operations is different.

ETL​

ETL stands for Extract, Transform, Load. In this approach, the data is transformed first before being loaded into the data warehouse.

Pros:

  • Cleaned and transformed data is directly loaded, reduces storage costs.
  • Easier to manage compliance and security, as sensitive data can be excluded before loading.

Cons:

  • Requires separate systems for transformation, increases complexity and costs.
  • Cannot easily reprocess data without going back to the source system.

ELT​

ELT stands for Extract, Load, Transform. In this approach, the data is loaded into the warehouse first and then transformed.

Pros:

  • No need for a separate transformation system; uses the resources of the data warehouse.
  • Easier to rerun transformations without impacting source systems.
  • Good for near real-time processing since loading data is faster.

Cons:

  • Requires more storage as full copies of data are stored.
  • More attention is needed to meet compliance standards for sensitive data.

The Cloud and ELT​

The growth of cloud data warehouses has made ELT even more popular.

  • Cloud storage offers nearly unlimited space for data.
  • Parallel computing power speeds up transformations, makes ELT more efficient.

In the cloud, you can store and transform vast amounts of data quickly, without worrying about hardware limitations.