SQL Error Handling: Logging Errors

Why Log Errors in SQL?

Logging errors allows developers and DBAs to capture detailed information about failures during SQL execution. This information is invaluable for troubleshooting and improving system stability.

Without error logging, diagnosing problems can be time-consuming and error-prone.

• Tracks when and where errors occur.
• Records error messages and codes for analysis.
• Helps identify recurring issues.
• Supports auditing and compliance requirements.

Implementing Error Logging Using TRY...CATCH

Most modern SQL dialects support TRY...CATCH blocks to handle errors gracefully. Within the CATCH block, you can capture error details and insert them into an error log table.

This approach prevents abrupt termination of scripts and allows controlled error management.

• Wrap your SQL statements inside a TRY block.
• Use the CATCH block to capture error information.
• Insert error details such as error number, message, severity, and timestamp into a log table.

Creating an Error Log Table

An error log table stores error details for later review. It typically includes columns for error number, message, severity, procedure name, line number, and timestamp.

Design your error log table to capture all relevant information to aid in debugging.

• ErrorNumber (int): The error code.
• ErrorMessage (nvarchar): The descriptive error message.
• ErrorSeverity (int): Severity level of the error.
• ErrorState (int): State code of the error.
• ErrorProcedure (nvarchar): The procedure where the error occurred.
• ErrorLine (int): Line number in the SQL code.
• ErrorTime (datetime): Timestamp of the error occurrence.

Example: Logging Errors in SQL Server

Here is a practical example that creates an error log table and uses TRY...CATCH to log errors during an INSERT operation.