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Data warehouse by Hung To Hanoi, 01st Sept 2011

Agenda Why we need the data warehouse ? The different between data warehouse and Relational DB Some popular architectures

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Why we need data warehouse ?

From history perspective The “dark ages”: information is stored in paper The “golden ages”: database are everywhere  Transactions are tracked  Stored data provides detailed history of transaction for report purpose

The next step: use data for decision-making  The needs of decision-making support system

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From history perspective Example: How to increase the sales of milk ?  Supply & Demand Principles  Manager does not want to decrease the price of milk  Market Basket Analysis: if you buy a certain group of items, you are more (or less) likely to buy another group of items  We Should decrease the price of bread by 5%

→ Question: What is the next generation after Data warehouse ?

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Different between Data Warehouse vs Relational DB The relationship between OLAP system and OLTP system

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The different between DW and Relational DB Data Warehouse ( for OLAP )

Relational DB ( for OLTP )

The Purpose

To support the analysis of business processes

To support the execution of business processes

The Data

Multi-dimensional views of various kinds of business activities ( current and history )

a snapshot of ongoing business processes ( Current )

Inserts and Updates

Does not update or insert data

Short and fast inserts and updates initiated by end users


Often complex queries involving aggregations (Unpredictable & Changing )

Relatively standardized and simple queries Returning relatively few records (Predictable & stable)

Process Time

Many hours: Batch data refreshes and complex queries

Typically very fast

Database Design

Typically de-normalized with fewer tables; use of star and/or snowflake schemas

Highly normalized with many tables (3NF)

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Popular Architectures of DW Inmon’s Corporate Information Factory

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Popular Architectures of DW Dimensional data warehouse advocated by Kimball

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Popular Architectures of DW Stand-Alone Data Marts ( Island of information )

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Thank you for listening Q&A

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