discuss time variant databse system.
discuss time variant databse system.
"Time variant" means that the data warehouse is entirely contained within a time period. Another way of stating that, is that the DW is consistent within a period, meaning that the data warehouse is loaded daily, hourly, or on some other periodic basis, and does not change within that period.
A data warehouse is a subject-oriented, integrated, time-variant and non-volatile collection of data in support of management's decision making process. Subject-Oriented: A data warehouse can be used to analyze a particular subject area. Integrated: A data warehouse integrates data from multiple data sources.
- Data Cleansing Tools.
- Data Transformation and Load Tools.
- Data Access and Analysis (Query) Tools.
- On-line analytical processing (OLAP) tools provide complex on-line analysis against live data.
- Multi-dimensional OLAP (MOLAP) tools were the first OLAP tools to be developed.
Data warehouses are used for analytical purposes and business reporting.
Data warehouses typically store historical data by integrating copies of transaction data from disparate sources.
Data warehouses can also use real-time data feeds for reports that use the most current, integrated information.
Time variance allows us to join transaction to reference data that contains values representative of the time of the event.
For example:
When a customer changes their address in a sales system, that sales system would just update the address. A data warehouse though would have processes that detect that change and then track that change allowing us to see the customers address before and after that change.
This allows us to then tie any sales events to the customer information that was active at the time of the sales event. This would allow you to report sales totals by the city of where the customers lived at the time of the sale, as opposed to sales by city based on where everyone currently lives
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