What is ETL & ELT? What is the diffrence between ETL & ELT?

The data is mine and  get value day by day on this century and last quarter of last century. Most of firm is race to mine and sell this mine.
In 1970's with the computers were used, the firm wanted to store and use the existing data and this way ETL emerged.

What is ETL?

It is about Extract - Trnsform - Load.

• Extract : Getting raw data according to requested criteria from some sources like; txt           files,applications (CRM, ERP), databases, vs. 
• Transform : On this session raw data is organized, cleared, aggregated and to applied some business rule. And then we can reach the enriched, clear, precious data.
• Load : On this part we write the precious data to target db or dwh.

What is ELT?

Elt is a new approach with the changing place of "L". Struct of Extract - Load - Transform is differ from T. The T take place in server on the ETL but on the contrary it is run on the target system on ELT.

All Secret in 'T'!
About the ETL & ELT is the changed place of T.

• When T is run?
• Where T is run?

ETL tools arose as a way to integrate data to meet the requirements of traditional data warehouses powered by OLAP data cubes and/or relational database management system (DBMS) technologies, depending on the architecture of the warehouse.  But in the meantime data has to proceed on T.

• Converting numeric values,
• Editing text string,
• Find and replace whatever wanted from you.
• Combine columns from diffrent tables and dbs
• Calculating aggregates

Changing and developing tech is allow to happen these steps on the target system, that is ELT.

How to make decission ETL or ELT?

Companies decide according to team and infrastructure.
- Underlying storage technologies,
- Design of DWH,
- How to use DWH by business

What is the diffrence between ETL & ELT?
It will continuou...