What are the benefits of using Slowly Changing Dimension Type 2?

1 What is SCD type 2?

SCD type 2 is a method of handling changes in dimension attributes by creating a new record for each change, and keeping the old record as well. This way, you can preserve the history of the changes and also maintain the current state of the dimension. For example, if a customer changes their name or address, you can create a new record for the customer with the new name or address, and keep the old record with the old name or address. To distinguish between the records, you need to add some additional columns to the dimension table, such as a surrogate key, a start date, an end date, and a current flag. The surrogate key is a unique identifier for each record, the start date and end date indicate the validity period of each record, and the current flag indicates whether the record is the latest or not.

2 Why use SCD type 2?

SCD type 2 has several benefits for data warehousing, such as the ability to track changes in dimension attributes over time and analyze their effect on facts and measures. This type of SCD also enables point-in-time analysis and comparison of data at different time periods. Additionally, SCD type 2 preserves the integrity and consistency of the data warehouse, as it does not overwrite or delete any records. Finally, it simplifies the loading and updating process of the data warehouse, as it only requires inserting new records for changes, instead of updating or deleting existing records. This reduces complexity and risk of errors in the data warehouse.

3 How to implement SCD type 2?

To implement SCD type 2 in your data warehouse, you need to identify the dimension attributes that are subject to change over time and decide which ones you want to track the history of. Additionally, add some additional columns to the dimension table to store the surrogate key, the start date, the end date, and the current flag. This can be done by using an ETL tool or a SQL script, which will extract data from the source systems and compare it with existing data in the dimension table. If there is no match, then a new record with new data is inserted; if there is a match, then changes in the dimension attributes are checked. The surrogate key is used to join the dimension table with the fact tables, and the start date and end date are used to filter and query data based on time period of interest. This process helps to inform and reassure stakeholders while providing valuable insights for improving cloud security posture.

4 What are the challenges of SCD type 2?

SCD type 2 can present a few challenges, such as increasing the size and complexity of the dimension table, which can have a negative impact on performance and storage of the data warehouse. It can also introduce some ambiguity and inconsistency in the dimension attributes, making data accuracy and reliability more difficult to achieve. In addition, it can complicate reporting and analysis, as it requires more logic and criteria to select and display the correct records. This can lead to a decrease in usability and flexibility of the data warehouse. All of these issues may require more maintenance, tuning, validation, cleansing, training, and documentation.

5 How to overcome the challenges of SCD type 2?

To overcome the challenges of SCD type 2, you can adopt some best practices. For example, use SCD type 2 only for the most relevant and important dimension attributes to reduce records and columns in the dimension table. Additionally, use a consistent and standard format and convention for the dimension attributes with rules and validations to ensure quality and consistency. Lastly, use a user-friendly and intuitive reporting and analysis tool that can handle the SCD type 2 logic and criteria to simplify and enhance reporting of the data. These practices can improve performance, storage, accuracy, reliability, usability, and flexibility of the data warehouse.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?