How to Calculate 5 Year and 10 Year Moving Averages in SQL: Step-by-Step Guide

Discover how to resolve SQL errors while calculating `5 year` and `10 year` moving averages using a structured SQL query with examples and explanations.
---
This video is based on the question stackoverflow.com/q/76993898/ asked by the user 'SJG' ( stackoverflow.com/u/22450978/ ) and on the answer stackoverflow.com/a/76993947/ provided by the user 'Tim Biegeleisen' ( stackoverflow.com/u/1863229/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Facing an issue while performing 5 year and 10 year moving average?

Also, Content (except music) licensed under CC BY-SA meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Calculate 5 Year and 10 Year Moving Averages in SQL: Step-by-Step Guide

Calculating moving averages is a common task in data analysis, especially when working with time-based data. In this guide, we will explore how to compute 5 year and 10 year moving averages using SQL. We'll take a look at an example that originated from Excel and guide you through the SQL implementation, while also addressing issues you might encounter along the way.

The Problem: SQL Error in Moving Average Calculation

When attempting to calculate the moving averages for a dataset that lists monthly totals over multiple years, you may encounter an error. Below is the error message related to the original SQL query:

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

This error arises because of a naming conflict between the Common Table Expression (CTE) and the original table name. Below, we will discuss the solution to this problem in detail.

Solution: Correcting the SQL Query

Step 1: Understanding the CTE

In SQL, a Common Table Expression (CTE) is a temporary result set that you can reference within a SELECT, INSERT, UPDATE, or DELETE statement. However, a CTE must not have the same name as the tables or views involved in its creation.

Step 2: Correcting the Query

To resolve the issue, we need to give the CTE a unique name instead of using the same name as the original table. Here is how you can structure the corrected SQL query:

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

Key Changes Added

Unique CTE Name: Changed the CTE name from MovingAverages to cte to avoid any conflicts.

Use of CASE Statement: The CASE statements ensure that only non-null values are displayed for moving averages, while rounding them to two decimal places for better readability.

Understanding the SQL Logic

Partitioning Data: The PARTITION BY MonthName clause ensures that the moving averages are calculated for each month separately.

Windowing Functions:

ROWS BETWEEN 4 PRECEDING AND CURRENT ROW calculates the average for the past 5 years, including the current row.

Similarly, ROWS BETWEEN 9 PRECEDING AND CURRENT ROW calculates the average over 10 years.

Conclusion

Calculating moving averages in SQL can be a straightforward task if the SQL syntax is correctly structured. By acknowledging and fixing naming conflicts, you can efficiently implement moving averages for your datasets.

Additional Tips

Always ensure your CTE names do not conflict with existing tables to avoid recursive clause errors.

Test your queries incrementally to easily identify issues.

Happy querying!