ETL stands for Extract, Transform, and Load. Extract is the process of fetching data from different data sources, Transform is the step where we apply transformation to data, such as aggregation, join with other datasets, applying rules, split or merge result set, and so on. In the Load step, we have data that is ready for the destination table structure, and we load that into the destination fact or dimension table in the data warehouse.

Data transfer or ETL is an important component of the BI and data warehousing system because the source data should be loaded into the data warehouse in a consistent way and be reliable. There are some concerns about data transfer, which makes this process even more important; data might come from different sources such as an Excel file, a DB2 database, or a web service, so the extract step should be able to pick data from all these kinds of data sources. In the transformation step, we should be careful that this...