Live ORACLE

DECLARE
 out_of_stock  EXCEPTION;
 number_on_hand  NUMBER := 0;
BEGIN
 IF number_on_hand < 1 THEN
   RAISE out_of_stock; -- raise an exception that we defined
 END IF;
EXCEPTION
 WHEN out_of_stock THEN
   -- handle the error
   dbms_output.Put_line('Encountered out-of-stock error.');
END;
/  

Encountered out-of-stock error.

PL/SQL procedure successfully completed.

Using RAISE to Force a User-Defined Exception