Understanding a Dimensional Data Warehouse

Many BI systems have a dimensional data warehouse as their data storage and retrieval layer. The data warehouse is stored in a relational database management system (RDBMS). At a very simple level, you can think of a relational database as a set of tables. Each table has rows and columns, like an Excel spreadsheet. In a dimensional data warehouse, dimensions are stored in dimension tables. Measures are called facts and are stored in fact tables.

A Fact Table

In a dimensional data warehouse, a table that stores the detailed values for measures, or facts, is called a fact table. Table 1-14 gives a conceptual view of the first few rows of the FactSales fact table. It stores Units Sold and Sales Dollars by ...

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