- · Subject-Oriented: A data warehouse can be used to analyze a particular subject area. For example, "sales" can be a particular subject.
- · Integrated: A data warehouse integrates data from multiple data sources. For example, source A and source B may have different ways of identifying a product, but in a data warehouse, there will be only a single way of identifying a product.
- · Time-Variant: Historical data is kept in a data warehouse. For example, one can retrieve data from 3 months, 6 months, 12 months, or even older data from a data warehouse. This contrasts with a transactions system, where often only the most recent data is kept. For example, a transaction system may hold the most recent address of a customer, where a data warehouse can hold all addresses associated with a customer.
- · Non-volatile: Once data is in the data warehouse, it will not change. So, historical data in a data warehouse should never be altered.
Types of Data Warehouse
Information processing, analytical processing, and
data mining are the three types of data warehouse applications that are
discussed below:
- · Information Processing - A data warehouse allows to process the data stored in it. The data can be processed by means of querying, basic statistical analysis, reporting using crosstabs, tables, charts, or graphs.
- · Analytical Processing - A data warehouse supports analytical processing of the information stored in it. The data can be analyzed by means of basic OLAP operations, including slice-and-dice, drill down, drill up, and pivoting.
- · Data Mining - Data mining supports knowledge discovery by finding hidden patterns and associations, constructing analytical models, performing classification and prediction. These mining results can be presented using the visualization tools.
Need for Data Warehouse
- · Provides an integrated and total view of the enterprise
- · Makes the enterprise’s current and historical information easily available for decision making
- · Makes decision-support transactions possible without hindering operational systems
- · Renders the organization’s information consistent
- · Presents a flexible and interactive source of strategic information
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