ETL Using Pentaho(Spoon)


Ralph Kimball who is well known as data warehouse architect. Kimball model based on dimensional model. In 1996, Kimball coined the concept called slowly changing dimension (SCD).

 What is SCD?

In the data warehouse, dimension attributes and their values slowly change over the period of time. Because data warehousing is time variant, it will store historical data at least more than 10 years data. 

In the Staff dimension table, some attributes may change over the period of the time without any prediction or condition.  For example

·         Years of Experience will change after some years in the Staff  dimension table.

·         Qualification of the staff to be modified

·         Designation of the staff

·         Add new column like alternative email_id in dimension table

·         Delete some values which is not relevant.

 The above mentioned are some of the examples of the SCD, based on modifications the SCD technique types are categorized. 

There are various types of SCD  technique are categories, such as

SCD Type 1 - New information simply overwrites the original information, don't keep old history or previous value of the record

SCD Type 2 -A new record is added into the existing dimension table.

SCD Type 3-The original record is modified to reflect the change.


Return to top