SCD - Type 1

Type 1 - Overwrite: In this approach, when changes occur, the existing values are overwritten with the new values. No historical data is preserved.

Before the change, the Product dimension table looks like this:

Product_ID	Product_Name	Category	Price
1	Smartphone	Electronics	800

After the change, the Product dimension table will look like this:

Product_ID	Product_Name	Category	Price
1	Smartphone	Mobile Devices	800

With a Type 1 SCD approach, the table now reflects the updated category for the "Smartphone" product. However, there is no record of the product's previous category, "Electronics," in the table.

Use Cases:

1. When historical data is not essential for analysis, and only the current values are needed.

2. For dimensions where tracking historical changes is not required for the business, such as minor corrections or updates to attributes.

3. In cases where the data warehouse is required to support reporting and analysis on the current state of the business, and not historical trends.

Advantages:

1. Simplicity: SCD Type 1 is relatively simple to implement, as it only requires overwriting existing records when changes occur.

2. Space Efficiency: Since there is no need to store historical data or multiple versions of records, the dimension tables will be smaller and require less storage space.

3. Performance: As there are no additional rows or columns for historical data, the querying and processing of the data warehouse will generally be faster.

Disadvantages:

1. Lack of Historical Data: SCD Type 1 does not store any historical data, which means it cannot support reporting and analysis that requires tracking changes over time. This can be a significant limitation for businesses that need to analyze trends, understand the impact of changes, or perform other historical analyses.

2. Loss of Previous Data: Since the dimension table only contains the most recent values, any changes that have occurred over time overwrite the previous values. This may lead to a loss of potentially valuable historical information.

3. Inability to Track Changes: With SCD Type 1, it is impossible to determine when or why changes occurred, as there is no record of any changes in the dimension data. This can make it challenging to understand the reasons for changes or identify any potential issues or patterns.