What is ETL or Extract, Transform, and Load?

To be able to understand ETL better, it’s best to first briefly say what a data warehouse is.  When you talk about Data Warehouse, what you’re actually talking about is the place where you keep all your data – electronically, that is.  However, your data warehouse isn’t only the place where you store all the electronic data you’ve gathered and now want to keep for future use.  It’s not like a garage where you carelessly throw in everything you’ve gathered.  Your data warehouse should be [...]