SCDs

In data warehousing, an SCD is used to manage infrequent changes to the values of a business entity over time, as opposed to changes that occur on a set schedule. Star schema design theory defines various types of SCDs, with Type 1 and Type 2 being the most common. In practice, a dimension table may support a combination of SCD types, such as Type 3 and Type 6, for tracking historical changes. Understanding the differences between these SCD types can be useful for designing an effective data warehousing solution.

Type 1 SCD

A Type 1 SCD design approach updates the dimension table with the most recent changes every time updates in the sources are seen. This method is typically used for storing supplementary values such as email addresses or company names of customers. If a customer’s contact information is altered, an update will be made to the dimension table to reflect the changes. The key of the table, such as CustomerID, will remain unchanged, ensuring that links...