This ETL process extracts medical insurance data from multiple databases, transforms it and loads it into a multi-dimensional data warehouse. The point of this process is to assign each individual to a category based on if they are consumer or corporate clients, what insurance they have, if they are self-funded versus fully insured, and if they opt to pay through their insurance plan or on a cash basis. The challenge in this ETL is that not all the required data is available due to a non-existent integration solution from major insurance companies. Several steps in the process are forced to make assumptions based on very specific conditions. Additionally, the different categories have certain rules that are not consistently applicable, which necessitates the creation of a large set of similar but different categories to handle the subtle differences between some types of customers.