What is the best way to learn extract, transform, and load process?

Extraction : It is the process of extracting data from different source file such as XML, excel, flat ....

Transformation: In this process data conversion take place such as string to int or date as per requirement.

Loading: It rear and final step to pour data in data base

 

We have lots of ETL technologies such as SSIS, TalenD, Informatic etc... most of them are free source except SSIS which is Microsoft product (Incensed ).

if you are a beginner it is better to learn from You tube.

there are many tools available in market.
most reasonable and leading in market is Informatica (9.0).
Download it from Oracle website and watch Tutorials on Youtube.
Regards

id suggest you to download an open source ETL tool and start to develop flows with it if you need help in that mail me.
thanks