What is Extract Transform Load

Posted By : Rashmi Verma | 09-Jun-2016

What is ETL ?

ETL stands for "Extract-Transform-Load" and it define the process how data is loaded from source system to the data warehouse.  In this Data is extracted from OLTP online transaction processing database, it transformed to match the data warehouse schema and loaded into the data warehouse database.  Data warehouses also combine data from non-OLTP systems like text files, preadsheets, legacy systems. ETL can Transform dissimilar data set into the unified data set.

 

ETL  Process - 

 

Extract - Extract data from the source system

Cleaning of data -  After data extraction it move to the cleaning and conforming phase . In the cleaning phase error are identify and fixing the error. In the conforming phase resolve the conflicts between those data’s that is incompatible, so that they can be used in an enterprise data warehouse.

Transform - In this data is transform in the dataware house format. It also builds the keys datawarehouse owns keys(primary, alternate key, foreign key, composite key) and never allows any other entity to assign them.

Load - Load data into the warehouse and creating an aggregate is summarizing and storing data which is available in fact table in order to improve the performance of end-user queries.

 

ETL testing is performed in five stages

  1.  Identifying data sources and requirements
  2. Data acquisition
  3. Implement business logics and dimensional Modelling
  4. Build and populate data
  5. Build Reports

 

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Rashmi Verma

Rashmi is a ISTQB Certified QA Engineer and with skills in Testing.

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