What is ETL?

Extract, Transform and Load (ETL) refers to the process in data warehousing that concurrently reads (or extracts) data from source systems; converts (or transforms) the data into the proper format for querying and analysis; and loads it into a data warehouse, operational data store or data mart. ETL systems commonly integrate data from multiple applications or systems that may be hosted on separate hardware and managed by different groups or users. ETL is commonly used to assemble a temporary subset of data for ad-hoc reporting, migrate data to new databases or convert database into a new format or type.