PL-SQL User Defined Exception

Using Variable of EXCEPTION type

DECLARE
	num1 NUMBER := 20;
	num2 NUMBER := 0;
	num3 NUMBER;
	divide_by_zero EXCEPTION;
BEGIN
	IF num2 = 0 THEN
		RAISE divide_by_zero;
	END IF;
	
	num3 := num1 / num2;
	DBMS_OUTPUT.PUT_LINE('Result : ' || num3);
	EXCEPTION WHEN divide_by_zero THEN
	DBMS_OUTPUT.PUT_LINE('Divide by Zero Exception');
END;
/

RAISE_APPLICATION_ERROR

The error number can be between -20,000 and -20,999.
SQLERRM is an utility class that is used to display the error message. SQLCODE is used to display the error code
We cannot name the exception using this approach

Declare User-Define Exception In Oracle Database | RebellionRider

SET SERVEROUTPUT ON;
 
ACCEPT user_input NUMBER PROMPT 'Enter your age ?';
DECLARE
	num1 NUMBER := &user_input;
BEGIN
	IF num1 < 18 THEN
		RAISE_APPLICATION_ERROR(-20000, 'You are underage');
	END IF;
 
	DBMS_OUTPUT.PUT_LINE('Hello user');
	EXCEPTION WHEN others THEN
	DBMS_OUTPUT.PUT_LINE(SQLERRM);
END;
/

PRAGMA EXCEPTION_INIT function

It is used to create named exception

SET SERVEROUTPUT ON;
 
DECLARE
	ex_age EXCEPTION;
	num1 NUMBER := 17;
	PRAGMA EXCEPTION_INIT (ex_age, -20000);
BEGIN
	IF num1 < 18 THEN
		RAISE_APPLICATION_ERROR(-20000, 'You are underage');
	END IF;
 
	DBMS_OUTPUT.PUT_LINE('Hello user');
	EXCEPTION WHEN ex_age THEN
	DBMS_OUTPUT.PUT_LINE(SQLERRM);
END;
/