How to Calculate Cumulative Sum by Month and User in Oracle SQL

Learn how to effectively use Oracle SQL's analytical functions to calculate the `cumulative sum` of points for each user by month. This guide includes step-by-step explanations and examples.
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Calculating Cumulative Sum by Month and User in Oracle SQL

When it comes to analyzing user behavior over time, aggregating data correctly is crucial. A common requirement is to calculate the cumulative sum of points earned by users in a particular period, usually broken down by month. Unfortunately, writing the right SQL query can sometimes be complex and might lead to unexpected results if not done properly. In this guide, we will explore how to achieve this in Oracle SQL.

Understanding the Problem

Let's first examine the scenario. You have a table that provides the points earned by various users across different months and years, as illustrated below:

USERYEARMONTHPOINT120201122020113202010120202122020203202021120203122020303202031From this data, you need to transform it into a cumulative format, like so:

USERYEARMONTHPOINT120201112020211202032220201122020212202031320201032020213202032To achieve this transformation, we will use analytical functions in SQL.

Solution: Using Analytical Functions

In order to create a cumulative sum by user, you'll need to leverage the SUM function combined with analytical features. Here’s how to do it:

Step 1: Basic Structure of the SQL Query

Your initial attempt used a query structure, but it didn’t yield the intended outcome. Here's a simplified query to achieve the desired result:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Adjusting Your Original Query

You'll just need to make a small adjustment to the SUM function you used in your original query. Specifically, by including the PARTITION BY clause, you can ensure the cumulative sum calculates correctly per user:

[[See Video to Reveal this Text or Code Snippet]]

Key Points to Remember:

The PARTITION BY clause divides the result set into partitions to which the function is applied. In this case, we are partitioning by USER to keep the cumulative scores separate for each user.

The ORDER BY clause determines the sequence in which the cumulative sum is calculated (i.e., by year and month).

Conclusion

By following the steps outlined above and making use of Oracle SQL's analytical functions, you can effectively calculate a cumulative sum of points for each user by month. This not only makes your data more understandable but also adds depth to your analysis. If you run into any challenges with your SQL queries, don’t hesitate to seek help or consult documentation—there's always a solution with the right approach!