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What is Data warehouse

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1. A data warehouse is the main repository (collection of resource which can be accessed to retrive information of an organization.


2. It usually contains historical data derived from transactional system.


3. Subject-oriented - A data warehouse can be used to analyize the particular subject area for example (finance,sales,hr,inventory)


4. Integrated - A data warehouse integrates data from mulitple data source.For example in an orginazation you may have integrated many product for transcation system(OLTP). But will find only one data warehouse product integrated for decsion support system(DSS)


5. Time-varient - Historical data is kept in data warehouse . For example one can retrive data 1 month or 3 month or 6 month or even older data from data warehouse. This contracts with trancation system, were offen most recent. For example if you see in trancation system regaring customer, it will have most recent data in it,were in data warehouse it will have all addresses accociated with the customer


6. Non volatile - Once you brough data inside data warehouse, It will not change. so, historical data in data warehouse should never be altered.


7. Data warehouse mainly used to retrive historical data in an orginazation with fastest retrival spead.


8. Data warehouse is mainly used by high level management for decision making.

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