ETL and ELT: Moving Data Between Systems
Businesses rarely keep all their data in one place. Sales might live in one system, marketing in another and finance in a third. ETL and ELT are the standard patterns for pulling that data together so it can be analysed as a whole.
The acronyms sound technical, but the idea is straightforward once the three steps are explained.
The Three Steps
- Extract: pull data out of each source system.
- Transform: clean, reshape and standardise it so it fits together.
- Load: place it into the destination, usually a data warehouse.
ETL vs ELT
ETL transforms data before loading it; ELT loads the raw data first and transforms it inside a powerful warehouse. Modern cloud warehouses make ELT increasingly popular because they can crunch large volumes cheaply.
| ETL | ELT | |
|---|---|---|
| Transform happens | Before loading | After loading |
| Best with | Smaller, complex feeds | Large cloud warehouses |
| Raw data kept | Often not | Yes |
Frequently Asked Questions
How often does this run?
It can be scheduled nightly, hourly or near real time, depending on how fresh your reports need to be.
If you need a hand with any of this, your Progressive Robot delivery team is ready to help. Raise a ticket from the Support area of your client portal or speak to your account manager and we will guide you through the next steps.