As you learned in Chapter 1, Data Warehouse Design, a data warehouse is an integrated database with a specific design, which helps us in data analysis and reporting. Chapter 1, Data Warehouse Design was about designing the data warehouse. However, there is always another step, that is, loading the data into the data warehouse. This requirement brings another component of the data warehousing system into play, which is Extract, Transform, and Load (ETL). The following list explains the function of each process:
Extract: This is the process of fetching data from the source systems
Transform: This is the process in which we apply transformations such as aggregation, joining with other datasets, applying rules, splitting or merging results, lookup, join, pivot, and many others
Load: This process is about loading data into the data warehouse destination tables such as fact and dimensions
There are a bunch of ETL tools that provide useful features...