SQL: Error Messages and Error Handling
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This document discusses SQL Server error messages, including how to generate common error types, the basic layout of error messages, how to create custom error messages, and techniques for handling errors like setting the XACT_ABORT option and using TRY/CATCH blocks. Error messages include a number, state, and severity level between 1-25 with higher numbers indicating more severe errors. Custom errors require the SysAdmin role and can include parameters and state information.
SQL: Error Messages and Error Handling
- 1. Presented by Aaron Buma
- 2. Error Messages – How to get them CREATE objects that already exist Violating Foreign Keys Exceeding permissions Trying operations that aren’t allowed (PRINT in a UDF)
- 3. Error Messages – Basic layout Message Number Number 50,000 for custom messages (default) State – You can track error locations with custom errors Severities 1-10: Status Info (Not Bad) 11-16: Can be corrected by the user (Fixable) 17-19: Errors with SQL Resources (Bad) 20-25: System Problems, Fatal Errors (Really Bad)
- 4. Error Messages - Custom You create message and severity Only users with SysAdmin role or Alter Trace can use WITH LOG – writes to error log You can have parameters in the text You can use Profiler to watch for them Watch for message number ‘50,000’ or a specific State
- 5. Error Handling Statement Termination - skip statement, but continue Scope Abortion - Exit this object, but continue Batch Abortion - Stop calling object Connection Termination – Disconnect, rollback open Trans ~ Severity > 20
- 6. Error Handling - XACT_ABORT If ON and in a transaction, it will rollback transaction SET XACT_ABORT ON / OFF Errors with Severity 11-16 cause Batch Abortion
- 7. Error Handling - TRY and CATCH BEGIN TRY Have your statements in the TRY, including BEGIN TRANs BEGIN CATCH Run code when error encountered You have access to the error properties
- 8. Demo