Shrunken Rollup Changing Dimension

Ch.02: DWH | DWH Components | Data Modeling | Dimension Types

Lesson Notes

Shrunken Rollup Changing Dimension Lesson Notes:

  1. Presentation Mode
  2. Static Mode

Video

Shrunken Rollup Dimensions

  • Shrunken Rollup dimension is used for developing aggregate (higher level of summary) fact tables.

  • It required that the data model has a lower level of granularity.

    • We have a daily usage fact table, and we need to have a higher level of monthly usage. So, we use the monthly dimension to get a summary of the daily.

    • We have a daily usage fact table aggregated on area-id, and we need to create another summary table aggregated based on city id. So, the new grain level here is the new dimension for the city.

Shrunken Rollup Dimensions Cont.

In this example we use the AreaId and the relation with CityID for shrunken the dimension and do higher level of aggregations.

  • Order detail per AreaID
    OrderDate AreaID TotalOrders
    123456789 123 20
    123456789 123 30
    123456789 678 10
    123456789 678 12
  • City and Area relationship dimension
    AreaID AreaName CityID
    123 Al-Matareya 1
    678 Ain shams 1
  • City dimension
    CityID CityName
    1 Cairo
  • Order detail per CityID
    OrderDate CityID TotalOrders
    123456789 1 72

Previous Chapters

Overview | Ch.01: Intro

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