A data warehouse is a data storage technology that brings together data from multiple sources into a single system. It serves as a centralized data hub holding large amounts of historical data that users can query for the purpose of analytics.
While data warehouses are very useful for analysis of historical data, they typically have high storage costs, meaning that data must be carefully cleaned and structured to optimize storage space before being brought into a warehouse. This preprocessing makes it easy to query a data warehouse, but the removal of information from data records can limit the scope of future analysis. Because of this, one common problem with data warehouses is that they are structured to answer specific questions, but are not flexible enough to allow for other analysis if different questions arise in the future.