SCD type 4 – Fast growing dimension

In normal scenarios the dimension tables tend to grow slowly. That is the reason, they are called slowly changing dimensions. Example: Location attribute of a customer changes very rarely. However the salary band of a customer is likely to change every year. These type of attributes causes the customer dimension table to grow rapidly. SCD type 4 provides a solution to handle the rapid changes in the dimension tables. The concept lies in creating a junk dimension or a small dimension table with all the possible values of the rapid growing attributes of the dimension.
Example: Take a look at the following dimension attributes of customer

C_Id
Name
Location
Age_band
Salary_band

The age band and salary band are going to change frequently. So create a separate small dimension table with only these attributes. The number of possible values of age band will be around 20 and salary band will be around 30. The total number of rows in the new dimension table are 20×30=60.
The new tables are

Table name : customer
C_Id
Name
Location

Table name: customer_mini
M_id
Age_band
Salary_band

Fact table:
Id
C_Id
M_Id
----

The dimension key of the new table should be maintained in the fact table. This way we can handle the rapid changes in the dimension table.