Says who? Says me!
There is a received wisdom in the world of business intelligence that says you need a data warehouse in your business, but is this true? Why do you need a data warehouse?
The most important reason is to get a single version of the truth, or a single customer view.
In any business bigger than a micro business there will be multiple systems containing information about your customers. These may be sales transactions, customer service interactions, email campaigns and more. If these are all left siloed in your business then you have only a fragmented view of your customers behaviours. Different reports from different silos will contradict each other and confusion will reign. You will waste large amounts of time arguing about what is the truth, not once, but over and over.
The purpose of a data warehouse is to combine all these silos into one repository. You will still need to have the conversations about what is the truth – is Silo A more reliable than Silo B for this particular piece of information, address, date of birth or whatever, but you will only need to have that conversation once, or occasionally, not every time you see a report.
The case for data stewardship
Looking at it from another angle, creating a data warehouse drives a conversation within your business about what data you have and how to curate it. And curate is the important word. We live in a world of data that drives our business, and if this data is so important (and it is, stop reading if you believe otherwise) then it needs that curation and TLC. This is another purpose of your data warehouse.
The case for capturing everything
Another thing a data warehouse is, is a repository. A place to store data that you may not even know you need yet. Those logs from your website, do they contain valuable data?
Operational systems with well understood data, put it straight into the data warehouse
Operational systems with partially understood data, put it into a data lake type of repository where you can retrieve the data one day if it becomes useful.