This paper introduces to some of the important issues concerned with Data warehousing. With the advent of new technologies for data management, data warehousing strategies go on changing. This paper describes data warehouses, criteria related to it and key issues in data warehouse with case studies of different databases.
Data Warehouses are mostly populated with periodic migrations of data from operational systems. The second source is made up of external, frequently purchased, databases.
Examples of this data would include lists of income and demographic information. This purchased information is linked with internal data about customers to develop a good customer profile.