Data Warehousing ■ Data sources often store only current data,not historical data Corporate decision making requires a unified view of all organizational data, including historical data A data warehouse is a repository(archive)of information gathered from multiple sources,stored under a unified schema,at a single site Greatly simplifies querying,permits study of historical trends 。 Shifts decision support query load away from transaction processing systems Database System Concepts-7th Edition 11.8 @Silberschatz,Korth and SudarshanDatabase System Concepts - 7 11.8 ©Silberschatz, Korth and Sudarshan th Edition Data Warehousing ▪ Data sources often store only current data, not historical data ▪ Corporate decision making requires a unified view of all organizational data, including historical data ▪ A data warehouse is a repository (archive) of information gathered from multiple sources, stored under a unified schema, at a single site • Greatly simplifies querying, permits study of historical trends • Shifts decision support query load away from transaction processing systems