Dylan's BI Study Notes

My notes about Business Intelligence, Data Warehousing, OLAP, and Master Data Management

What are slowly changing dimensions?

Posted by Dylan Wan on January 11, 2007

Slowly changing dimensions are used to describe the date effectivity of the data. It describe the dimensions whose attribute value vary over time.

This term is commonly used in the Data Warehousing world. However, the problem exists in the OLTP, relational data modeling as well.

Example:

The sales representative assigned to a customer may change over time. Linda was the salesrep for ABC, inc. before March last year. Kathy later becomes the representative for this account.

You may want to track the data “as is”, “as was”, or both. If you show the year total sales, you can either report as the sales are all generated by Kathy, or actually break the number down between Linda and Kathy.

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