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.