Sunday, January 18, 2009

Define : SCD (Slowly Changing Dimensions)

SCD is abbreviation of Slowly changing dimensions in Data Warehousing.

SCD applies to cases where the attribute for a record varies over time. There are three different types of SCD.

a) SCD1 : The new record replaces the original record.
Only one record exist in database - current data.

b) SCD2 : A new record is added into the customer dimension table.
Two records exist in database - current data and previous history data.

c) SCD3 : The original data is modified to include new data.
One record exist in database - new information are attached with old information in same row.

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