Slowly Changing Dimensions

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  • Type 1 Slowly Changing Dimension data warehouse architecture applies when no history is kept in the database. The new, changed data simply overwrites old entries. This approach is used quite often with data which change over the time and it is caused by correcting data quality errors (misspells, data consolidations, trimming spaces, language specific characters).

    Type 1 SCD is easy to maintain and used mainly when losing the ability to track the old history is not an issue.

  • Slowly changing dimension Type 2 is a model where the whole history is stored in the database. An additional dimension record is created and the segmenting between the old record values and the new (current) value is easy to extract and the history is clear.

    The fields 'effective date' and 'current indicator' are very often used in that dimension and the fact table usually stores dimension key and version number.

  • Nice question. Thanks

    Jason...AKA CirqueDeSQLeil
    I have given a name to my pain...MCM SQL Server, MVP
    Posting Performance Based Questions - Gail Shaw[/url]
    Learn Extended Events

  • I look forward to Raju The Leader (???) enlightening us all about Type 3 SCDs :laugh:

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