Explain any two different characteristics of Data Warehouse. How is it different from the Data base.

Characteristics of data warehouse Subject oriented: A data warehouse is organized around major subjects such as customer, products, sales etc. Data is organized according to subject instead of application. For example, an insurance company using a data warehouse would organize their data by customer, premium and claim instead of by different product like auto, life etc. The data organized by subject obtains only the information necessary for the decision support processing. Integrated: A data warehouse is usually constructed by integrating multiple, heterogeneous sources such as relational databases, flat files and OLTP (On Line Transaction Processing) file. When data resides in many separate applications in the operational environment, the encoding of data is often inconsistent. When data is moved from operational environment into the data warehouse, they assume a consistent coding convention. Nonvolatile: A data warehouse is always a physically separate store of data, which is transformed from the application data found in the appropriate environment. Due to this separation, data warehouses do not require transaction processing, recovery, concurrency control, etc. The data is not updated or changed in any way once they enter the data warehouse, but are only loaded, refreshed and accessed for queries. Time variant: Data is stored in data warehouse to provide a historical perspective. Every key structure in the data warehouse contains, implicitly or explicitly, an element of time. The data warehouse contains a place for sorting data that are 5 to 10 years old, or older, to be used for comparisons, trends and forecasting. Database vs. Data warehouse Database is a collection of related information stored in a structured form in terms of table so that it makes easier insertion, deletion and manipulation of data. Database consists of tables that contain attributes. Whereas a data warehouse is a database system optimized for reporting and analysis. It generally refers to the combination of many different databases across entire enterprise. A data warehouse stores historical data so that one can analyze and extract insights from it. It does not store current information, nor is it updated in real-time. Once the data entered in the data warehouse, it can be then only loaded, refreshed and accessed for queries. Data warehousing emphasizes the capture of data from diverse sources for useful analysis and access, but does not generally start from the point-of-view of the end user who may need access to specialized, sometimes local databases.