ETL Testing

ETL stands for extraction, transformation and loading. ETL is a process that involves the following tasks:

  1. Extracting data from source operational databases(OLTP ) or Archive systems which are the primary source of data for the data warehouse
  2. Transforming the data - which may involve cleansing, filtering, validating and applying business rules
  3. Loading the data into a data warehouse or any target database(OLAP).

 The key idea:
a) Data integration :Collecting and combining the data from various sources  in order to provide standardized view of the data.
b)Data Migration:Transformaing and mapping between source and target structure  of DB tables .
In ETL approach the data will move from different source Databases to Data warehouse during this approach in intermediated stage the data will transform as per Business rules based on different dimensions and look up data.
Data from numerous sources is extracted, transformed and loaded into a single repository where it resides at query-time. When a query is submitted, the data warehouse locates the data, regains it and presents it to an end user as an integrated whole