Data Warehouse Database Design Methods For Technical IT Audience Peter Nolan

Agenda  DW design methods  Star Schemas  Why, What, Features?  Time Variant + Stability Analysis  Why and What?

DW Design Methods  Three different methods widely used  Choice of use depends on many factors  Star Schema  Transaction and ROLAP  Time Variance + Stability Analysis  Changes to non-txn data eg. Customer  Third Normal Form  Volumes of changes are low

Why Use Star Schemas?  Business people understand them!!  Matches the business model  Often intuitively obvious  Easy to query  Supports complex questions easily  No wrong answers due to join problems  Excellent performance on star schema aware databases  Oracle, Informix, DB2

What Does a Star Schema Look Like?

Some Useful Features  Multi-level summaries defined in control table  New summaries require NO code changes  Generated keys for customers and accounts  Demographic & Product Grouping for customers and accounts

Why Use Integer Keys?  Performance  Integers is the fastest data type to operate on  Space and throughput  Integers are shorter than account numbers  Disk savings in tables and indexes  Speed from disk to processor  Flexibility  Allows multi-level summary tables  No IT involvement to create new summaries!!  Large Stars!!

Why Use TV + SA?  “Be able to show me the value of any field at any time in the past”  Archival databases  When people really do not know what they want  Not easy to query  Cannot give this to business people

What Does TV + SA Look Like? Each 3NF entity passed to the DW is split into 3 (or more) entities based on stability analysis and access analysis. An element of time is added to the key.

Summary  DW design methods  Star Schemas  Why, What Features?  Time Variant + Stability Analysis  Why and What?

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