SQL Error Handling (TRY/CATCH / Exception blocks)

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🔊 Listen

When running SQL code, errors can happen — like constraint violations or syntax errors. Handling these errors gracefully lets you control what happens next instead of crashing your application or process.

🔹 Why Handle Errors?

• Prevent your transaction from failing unexpectedly
• Log or notify about issues
• Retry operations or clean up resources

🔹 Common Error Handling Methods by DBMS

🔹 Example: SQL Server TRY…CATCH

BEGIN TRY
    -- Attempt an operation
    INSERT INTO employees (id, name) VALUES (1, 'John');
END TRY
BEGIN CATCH
    -- Error handling logic
    PRINT 'Error occurred: ' + ERROR_MESSAGE();
    ROLLBACK TRANSACTION;
END CATCH;

🔹 Example: Oracle PL/SQL Exception Handling

BEGIN
    INSERT INTO employees (id, name) VALUES (1, 'John');
EXCEPTION
    WHEN DUP_VAL_ON_INDEX THEN
        DBMS_OUTPUT.PUT_LINE('Duplicate ID error.');
    WHEN OTHERS THEN
        DBMS_OUTPUT.PUT_LINE('Some other error occurred.');
END;

🔹 Best Practices

• Always handle exceptions where failure is possible
• Use specific exception/error codes when possible
• Roll back transactions if needed
• Log errors for debugging and auditing
• Keep error messages user-friendly and secure

🧠 Quick Recap

💡 Proper error handling makes your SQL code robust and your application reliable.