In Type 2 Slowly Changing Dimension, a new record is added to the table to represent the new information. Therefore, both the original and the new record will be present. The new record gets its own primary key.
In our example, recall we originally have the following table:
After Christina moved from Illinois to California, we add the new information as a new row into the table:
- This allows us to accurately keep all historical information.
- This will cause the size of the table to grow fast. In cases where the number of rows for the table is very high to start with, storage and performance can become a concern.
- This necessarily complicates the ETL process.
About 50% of the time.
When to use Type 2:
Type 2 slowly changing dimension should be used when it is necessary for the data warehouse to track historical changes.