Step-4: Handling Slowly Changing Dimensions

Option-1: Overwrite History

• Example: Code for a city, product entered incorrectly

• Just overwrite the record changing the values of modified attributes.

• No keys are affected.

• No changes needed elsewhere in the DM.

• Cannot track history and hence not a good option in DSS.

 The first technique is the simplest and fastest. But it doesn't maintain past history! Nevertheless, overwriting is frequently used when the data warehouse team legitimately decides that the old value of the changed dimension attribute is not interesting . For example, if you find incorrect values in the city and state attributes in a customer record, then overwriting would almost certainly be used. After the overwrite, certain old reports that depended on the city or state values would not return exactly the same values. Most of us would argue that this is the correct outcome.

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