# ETL and ELT — Data Warehousing & Modelling

Source: https://www.geekswithgeeks.com/en/data-warehousing/data-warehousing-03

> Apply ETL and ELT with a clear goal and verifiable outcome.

## Understand ETL and ELT

For **ETL and ELT**, begin with the problem it solves. Identify the input, the constraint, and the observable result before selecting a tool or workflow. This makes your choice explainable and easier to review.

## Practise deliberately

Create a small, safe example for **ETL and ELT**. Change one thing at a time and write down why the result confirms or disproves your assumption.

## A useful comparison

**ETL and ELT** is like a checklist before a journey: it cannot travel for you, but it prevents a small missed detail from becoming a costly surprise.

Check the reasoning behind the action.

**Quiz:** What is the strongest first step when using ETL and ELT?

- [x] Define the problem, constraint and evidence for success.
- [ ] Copy the largest example without reading it.
- [ ] Skip verification to save time.

*Answer:* Define the problem, constraint and evidence for success.. Clear constraints and a verifiable result make a workflow reliable.