Скачать или смотреть Understanding Trigger Failures in SQL Server: What Happens to Your Stored Procedure Updates?

Explore how trigger failures affect updates in SQL Server stored procedures, and learn how to manage them effectively.
---
This video is based on the question https://stackoverflow.com/q/64565895/ asked by the user 'mrivanlima' ( https://stackoverflow.com/u/11301220/ ) and on the answer https://stackoverflow.com/a/64566049/ provided by the user 'squillman' ( https://stackoverflow.com/u/75852/ ) 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: What if my trigger fails after an update inside a stored procedure?

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

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Trigger Failures in SQL Server: What Happens to Your Stored Procedure Updates?

When working with SQL Server, it’s common to encounter situations where triggers are tied to updates in stored procedures. However, what happens if a trigger fails after an update occurs within a stored procedure? This can lead to uncertainty and confusion. Let’s delve into this issue and clarify the mechanics of how SQL Server handles such situations.

The Issue at Hand

Question

Imagine you execute an update within a stored procedure successfully. However, due to a malfunction in the trigger designed to execute alongside this update, you might wonder: Will the update be rolled back?

The short answer is Yes. If the trigger encounters any runtime error or if a rollback is initiated within it, the entire transaction will roll back, impacting your update even if the update itself ran without a hitch.

A Detailed Explanation

Rollback Mechanism

In SQL Server, when a trigger fails, it influences the transaction of the statement that invoked it. Here’s how it works:

Trigger Activation: An AFTER UPDATE trigger runs whenever an update occurs on a specified table.

Error Encountered: If the trigger's code has an error or a rollback statement is executed within it, SQL Server will revert all changes made by the update, effectively rolling back the transaction.

Result: As a result, any changes that were supposed to be executed will not be reflected in the database.

Illustration of the Concept

Let’s illustrate this with a simple example. Here’s a demonstration of how the rollback operates in a typical scenario.

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

Analyzing the Results

After executing the code above, you’ll notice the following:

The value of ID in MyTable remains 1.

The OtherTable stays empty because the trigger generated an error, leading to a rollback of the update.

What About XACT_ABORT?

Even if you set XACT_ABORT OFF, the result remains unchanged. The rollback will still occur in response to an error within the trigger. For example:

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

Handling Trigger Failures Gracefully

If your intention is to allow the update to persist regardless of a trigger's failure, consider implementing a TRY/CATCH block within your trigger. This provides a mechanism to handle errors gracefully and allows the trigger to complete without affecting the overall transaction.

Example with TRY/CATCH

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

Conclusion

In summary, a trigger failing after an update in a stored procedure will indeed result in a rollback of the update transaction. Understanding this mechanism is crucial for database developers and administrators in SQL Server. By incorporating error handling strategies such as TRY/CATCH, you can gain more control over how triggers impact your transactions, leading to more robust and error-tolerant database applications.

If you’re wrestling with trigger management or rollback issues, keep this guide handy as a resource for smoother SQL operation.