The three layers in the ETL are:
Staging Layer : Staging layer is used to store the data which is extracted from the different data source systems.
Data Integration Layer : Integration layer transforms the data from the staging layer and moves the data to a database. In the database, the data is arranged into hierarchical groups, which is often called dimension, and into facts and aggregation facts. The combination of facts and dimension table in a data warehouse system is called a schema.
Access Layer : Access layer is used by the end-users to retrieve the data for analytical reporting.
