Data Warehousing:
Shifting data from transactional system to a data warehouse or a data mart allows you to secure your data and also gives you the functionality to retrieve trends and other business values from the historic data.
Business Intelligence would not be possible without data warehouses. But even data warehouses need to be tweaked to make them best suited for BI. The process is converting normalized tables to de-normalized form so that a dimensional model can be implemented in place of the typical ER model.
Dimensional Model allows for easier data retrieval and any user even with minimal technical knowledge can understand how data is saved using star schema.
Star Schema is composed of facts and dimensions. Fact is the numerical data field which is usually aggregated over the related fields. E.g. Sales
Dimensions are the related fields that give additional information about the fact field. E.g. ProductID, StoreID etc.
Indexing allows faster query fetching but slows the system by slowing update, delete append!!!
