11warehouse

11warehouse - CSE-5120-Fall-2009 Client Client Data...

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CSE-5120-Fall-2009 Data Warehousing Decision support systems (DSS) in business Also called On line analytical Processing (OLAP) (vs OLTP : On line transaction processing) Many corporations use data warehouses for their analysis. Decision support applications involve com- plex queries on very large database, re- sponse time should be small, E.g. R( Customer, District, Amount ) SELECT District, SUM(Amount) FROM R GROUP BY District The raw data is relational data raw data data cube data cube may be materialized (pre- computed and stored) Optimization: materialize some or all of these views rather than compute them from raw data each time. Which views to materialize when it is too expensive to materialize all views? Heterogeneous database Integration Goal: easy and e±cient access to inte- grated information from multiple, hetero- geneous, autonomous, distributed informa- tion sources. Info Source Info Source Info Source ... Client Client The Warehousing Approach Information integrated in advance Stored in warehouse for direct querying and analysis Info Source Info Source Info Source ... Client Client Data Warehouse Advantages of Warehousing Approach High query performance But not necessarily most recent state Doesn’t compete with local processing Information copied at warehouse Can modify, annotate, summarize, etc. Can store historical information 84
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The Data Cube E.g. Parts are bought from suppliers and then sold to customers at a sale price SP Suppliers Parts Customers sale price ALL SELECT Part, Customer, SUM(SP) FROM R GROUP BY Part, Customer Suppliers Parts Customers ALL collapse by SUM Part Supplier Customer ( P, ALL, C ) SELECT Part, SUM(SP) FROM R GROUP BY Part Parts Customers collapse by SUM Suppliers ( P, ALL, ALL ) (P, S, C) is a base cell in the data cube. (P, ALL, C) and (P, ALl, ALL) are aggregate cells. Cuboid Lattice
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This note was uploaded on 04/23/2010 for the course CSC CSC5120 taught by Professor Adafu during the Fall '09 term at CUHK.

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11warehouse - CSE-5120-Fall-2009 Client Client Data...

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