PL/SQL RAISE_APPLICATION_ERROR

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.