How Can SQL Server Extended Events Identify the SQL Statements Affecting a Specific Table?

Creating a Trigger to Capture Executed SQL for an Affected Table

Problem:

To troubleshoot mysterious updates to a particular table, it is necessary to identify the executed SQL that led to the changes. Unfortunately, the application's business logic primarily resides in the database, making it challenging to determine the source of these updates.

Objective:

Create a trigger on the table in question to log the SQL statements that affect it, enabling the identification of the culprit SQL.

Approach Using SQL Server Extended Events:

1. Setup Database for Testing:

Create a simple database with the necessary tables and triggers to simulate the problematic scenario.

2. Create Extended Event Session:

Use SQL Server Extended Events to capture the SQL statements executed against the table. This involves creating an event session that filters on the trigger being used to simulate the updates.

3. Trigger Proc1 Procedure:

Execute Proc1, which triggers a cascade of procedure calls that eventually causes the mysterious update to the table.

4. Stop Extended Event Session:

After the procedures have executed, stop the Extended Event session.

5. Analyze Event Data:

Use the fn_xe_file_target_read_file function to read the data captured by the Extended Event session and analyze the call stack to identify the executed SQL statements.

Advantages of Extended Events Approach:

• Captures all executed SQL statements, including stored procedures and triggers
• Provides detailed call stack information to track the execution path
• Doesn't require any code modification to the application

Additional Benefit:

The captured Extended Events data can also be used to troubleshoot performance issues by analyzing the query execution plans and execution statistics.

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