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Loading the Slowly Changing Dimension
Topic: Business Intelligence Files
Owner: Tim Gorman
Date: 2014-06-23
Subtopic: Kaleidoscope 2008

Designing tables for slowly-changing dimensions (SCDs) is one of the most difficult tasks in a database supporting BI/DW applications. SCDs can grow quite large; it is not unusual for some to contains hundreds of millions of rows, so how do we meet the performance requirements of the end-user queries against this monstrous object, and how do we do so while continuing to load large amounts of data to it? The answer lies in understanding how a time-variant SCD is queried, and then building an optimal table structure to meet each of those requirements. For example, the run-time users from the DW/BI application need to see the "type-2" or "type-3" time-variant view of the slowly-changing dimension, while the data-loading (ETL or ELT) processing needs to see the current point-in-time (i.e. "type-1") view of the SCD for loading new data. How can these differing requirements be satisfied by one table? Short answer: they cannot. This presentation provides a viable solution for consideration, complete with sample code for implementation.

Download File View File   TGorman KScope14 LoadSCD 20140623.pdf

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