In Oracle PL/SQL, error handling is crucial for building robust applications. One of the key mechanisms for managing custom errors is the RAISE_APPLICATION_ERROR procedure. This article explores its purpose, syntax, usage, and best practices.
What is RAISE_APPLICATION_ERROR?
RAISE_APPLICATION_ERROR is a built-in Oracle procedure that allows developers to raise custom error messages with user-defined error codes. It helps in managing application-specific exceptions that standard Oracle errors do not cover.
Syntax
RAISE_APPLICATION_ERROR(error_number, error_message [, keep_errors]);
Parameters:
error_number: A negative integer between -20000 and -20999 that uniquely identifies the error.
error_message: A string (up to 2048 bytes) containing the custom error message.
keep_errors (optional): A Boolean flag (TRUE or FALSE). When TRUE, it preserves existing error messages in the error stack. The default is FALSE.
Examples
1. Raising a Simple Custom Error
BEGIN RAISE_APPLICATION_ERROR(-20001, 'Invalid operation detected'); END;
This raises an error with code -20001 and message ‘Invalid operation detected’.
2. Using RAISE_APPLICATION_ERROR in Exception Handling
DECLARE v_salary NUMBER := 5000; BEGIN IF v_salary < 10000 THEN RAISE_APPLICATION_ERROR(-20002, 'Salary below the minimum threshold'); END IF; END;
If v_salary is below 10000, the procedure raises an error with the specified message.
3. Using RAISE_APPLICATION_ERROR Inside a Stored Procedure
CREATE OR REPLACE PROCEDURE check_employee_salary(p_emp_id NUMBER) AS v_salary NUMBER; BEGIN SELECT salary INTO v_salary FROM employees WHERE employee_id = p_emp_id; IF v_salary < 5000 THEN RAISE_APPLICATION_ERROR(-20003, 'Salary too low for employee ID: ' || p_emp_id); END IF; END check_employee_salary;
If the employee's salary is below 5000, the procedure throws a custom error.
4. Preserving Errors in the Stack with keep_errors
BEGIN BEGIN RAISE_APPLICATION_ERROR(-20004, 'First error'); EXCEPTION WHEN OTHERS THEN RAISE_APPLICATION_ERROR(-20005, 'Second error', TRUE); END; END;
Using TRUE as the third parameter keeps the first error in the error stack.
Best Practices
Use Meaningful Error Messages: Clearly describe the issue to help debugging.
Choose Unique Error Codes: Avoid conflicts with other custom errors.
Use Exception Handling Blocks: Combine with EXCEPTION blocks for controlled error management.
Avoid Overuse: Only raise errors when necessary to prevent unnecessary disruptions.
Document Errors: Maintain a list of error codes and messages for easy reference.
Conclusion
The RAISE_APPLICATION_ERROR procedure is a powerful tool for handling application-specific errors in Oracle PL/SQL. By using it effectively, developers can create more controlled, informative, and manageable error-handling mechanisms in their applications.