如果抛出异常，则没有返回值。引发异常，调用堆栈在此结束。
当然，您可以在函数中使用no_data_found：

CREATE OR REPLACE function get_employees (pID in varchar2) return Number 
As
salary Number;
begin

begin
select e.salary into salary from employees e where employee_id=pID;
EXCEPTION WHEN NO_DATA_FOUND THEN
salary := -1;
END;

return salary;

end get_employees;

CREATE OR REPLACE function get_employees (id in varchar2) return varchar2 is

   sal employees.salary%type;

begin

   select salary  into sal from employees where employee_id=id;

   return sal;

EXCEPTION WHEN NO_DATA_FOUND THEN
   raise_application_error(-20001, 'Custom NO_DATA_FOUND');    
end get_employees;

不能在函数中使用NO_DATA_FOUND，因为它将给予一个预定义的异常，用于空返回。

希望下面的例子有助于解决退货问题......

SET SERVEROUTPUT ON ;

    /

    CREATE OR REPLACE FUNCTION FN_CHK
    RETURN NUMBER
    IS   
        V_CHK NUMBER :=1;
    BEGIN
        FOR I IN 1..100
        LOOP
            DBMS_OUTPUT.PUT_LINE(I);
            IF(I>=4) THEN
                --DBMS_OUTPUT.PUT_LINE('BREAK');
                V_CHK:=0;
                --V_CHK:=0/0;
                exit;
            END IF;
        END LOOP;
        RETURN V_CHK;
      
    EXCEPTION WHEN OTHERS THEN
    V_CHK:=1000;  

    RETURN V_CHK;
    END;

    /

    SELECT FN_CHK
    FROM DUAL;