Resolving the ORA-00937: not a single-group group function SQL Error in Oracle

Опубликовано: 15 Апрель 2025
на канале: vlogize

Learn how to fix the common SQL error `ORA-00937: not a single-group group function` in your Oracle queries with an explanation and example.
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Fixing the ORA-00937: not a single-group group function Error in Oracle SQL

If you’re working with Oracle SQL and have encountered the error message SQL Error [937] [42000]: ORA-00937: not a single-group group function, you are not alone. This error typically arises when there is an issue with how aggregate functions and grouping are used in your query. In this post, we will discuss the cause of this error and how to resolve it effectively.

Understanding the Problem

When writing SQL queries, particularly those involving aggregate functions like SUM, you need to ensure that the query is structured properly, especially when using GROUP BY. The error you are experiencing occurs when Oracle expects a single grouped result but finds multiple possible results because of how the aggregate functions are applied.

Example of the Problematic Query

Here is the query that led to the error:

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

When executed, this query throws the ORA-00937 error due to the incorrect usage of the SUM function within the CASE statement.

How to Fix the Error

To resolve this issue, we need to modify the way the CASE statement and its aggregate functions are structured in the Common Table Expression (CTE).

Steps to Fix the Issue

Modify the CASE statement – We need to ensure that the CASE statement applies correctly within the aggregation context.

Adjust the aggregate functions – We ensure that the SUM function wraps the entire CASE expression to aggregate the result properly.

Here’s how you can modify that part of the query:

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

The Corrected Query

By applying these changes, your CTE would look like this:

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

Testing the Changes

After implementing the above adjustments, run your SQL query again. The error should be resolved, and the query should execute correctly, providing the expected aggregated results without further issues.

Conclusion

By understanding the cause of the ORA-00937: not a single-group group function error and applying the recommended fixes, you can handle this common SQL issue with ease. Always remember that when working with aggregate functions, proper grouping is essential to avoid ambiguity.

Feel free to reach out if you have any further questions or run into other SQL challenges!