A "data warehouse" is a system used for reporting and data analysis, and is considered a core component of business intelligence. DWs are central repositories of integrated data from one or more disparate sources. They store current and historical data in one single place" (Wikipedia). "Data warehousing is used to provide greater insight into the performance of a company by comparing data consolidated from multiple heterogeneous sources" (Investopedia).

"Data flows into a data warehouse from transactional systems, relational databases, and other sources, typically on a regular cadence. Business analysts, data scientists, and decision-makers access the data through business intelligence (BI) tools, SQL clients, and other analytics applications" (AWS). "Data warehouses can also feed data marts" (TechTarget), which are "subsets of data warehouses oriented for specific business lines, such as sales or finance. A data warehouse typically combines information from several data marts in multiple business lines, but a data mart contains data from a set of source systems related to one business line" (Panoply).

"A data warehouse is designed to support business decisions by allowing data consolidation, analysis, and reporting at different aggregate levels. Data is populated into the DW through the processes of extraction, transformation, and loading" (Techopedia).

Businesses employ data warehouses because "a database designed to handle transactions isn’t designed to handle analytics. It isn’t structured to do analytics well. A data warehouse, on the other hand, is structured to make analytics fast and easy" (HealthCatalyst) because they store data in a columnar database. "Data warehouses are used for online analytical processing (OLAP), which uses complex queries to analyze rather than process transactions" (Panoply).


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