A Slowly Changing Dimension (SCD) is a dimension that stores and manages both current and historical data over time in a data warehouse. SCDs are dimensions that contain data that changes slowly, rather than changing on a time-based, regular schedule. SCD is considered and implemented as one of the most critical ETL (Extract Transform Load) task in tracking the history of dimension records. There are three types of SCDs and you can use Warehouse Builder to define, deploy, and load all three types of SCDs. They are: