July 2010
Intermediate to advanced
840 pages
16h 33m
English
Content preview from Joe Celko's SQL for Smarties, 3rd Edition
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31.1. Star Schema
The Star Schema is a violation of basic normalization rules. There is a large central fact table. This table contains all the facts about an event that you wish to report on, such as sales, in one place. In an OLTP database, the inventory would be in one table, the sales in another table, customers in a third table, and so forth. In the data warehouse, they are all in one huge table.
The dimensions of the values in the fact table are in smaller tables that allow you pick a scale or unit of measurement on that dimension in the fact table. For example, the time dimension for the Sales fact table might be grouped by year, month within year, week within month. Then a weight dimension could give you pounds, kilograms, or stock packaging ...
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