Question

Explain slowly changing dimensions and its type with examples

Answer 1

dimensions that change slowly over time, rather than changing on regular schedule, time-base. In Data Warehouse there is a need to track changes in dimension attributes in order to report historical data. In other words, implementing one of the SCD types should enable users assigning proper dimension's attribute value for given date. Example of such dimensions could be: customer, geography, employee.

There are many approaches how to deal with SCD. The most popular are:

Type 0 - The passive method Type 1 - Overwriting the old value Type 2 - Creating a new additional record Type 3 - Adding a new column Type 4 - Using historical table Type 6 - Combine approaches of types 1,2,3 (1+2+3=6)