SCDs (slowly changing dimensions) are the dimensions in which the data changes slowly, rather than changing regularly on a time basis.
Three types of SCDs are used in Data Warehousing:
SCD1: It is a record that is used to replace the original record even when there is only one record existing in the database. The current data will be replaced and the new data will take its place.
SCD2: It is the new record file that is added to the dimension table. This record exists in the database with the current data and the previous data that is stored in the history.
SCD3: This uses the original data that is modified to the new data. This consists of two records: one record that exists in the database and another record that will replace the old database record with the new information.