Rapidly Changing Dimension

• Dimension where data changes are happening very rapidly
• "Slowly Changing Dimension" blog tells how we can maintain the history of changes
• But if we really implement the same technic for RCD, it will end up creating N number of Type-2 records for same entity and hence we need to come up with a smart design
• We can handle this by creating Junk Dimension
• Let's take an example of Customer Dimension, assume we have following columns
• CUSTOMER_KEY
• CUSTOMER_NAME
• CUSTOMER_GENDER
• CUSTOMER_MARITAL_STATUS
• CUSTOMER_TIER
• CUSTOMER_STATUS
• Now, Name, Gender, MaritalStatus gets a change very rare, once in a while but Tier & Status get the change very frequently, assume that we are not interested in historical changes of Name, Gender & Marital Status, holding only latest value should be fine, but we need to track the history changes of Tier & Status
• Now create a junk dimension by removing Tier & Status from Original Dimension
• So our Original Customer Dimension will be like this
• CUSTOMER_KEY
• CUSTOMER_NAME
• CUSTOMER_GENDER
• CUSTOMER_MARITAL_STATUS
• Create a new junk dimension for Tier, Status and create another mapping dimension, so overall structure will look like this

• By doing so, new type-2 record generation will happen only in a mapping table and not in the main table, so that way we can have easy mainteanance.
• Only disadvantage is - it will introduce extra joins to get the full picture of history changes of a particular customer
• But maintenance and storage vise, we will get benefits