declare 
v_count number;
begin 
select count(*) into v_count from dept;
if v_count  10 then 
raise_application_error(-20001,'数量小于10');
end if;
end; 

declare 
v_count number;
my_exp exception;
begin 
select count(*) into v_count from dept;
if v_count  10 then 
raise my_exp;
end if;
exception 
when my_exp then 
dbms_output.put_line('数量小于10');
when others then 
dbms_output.put_line('其他异常');
end;

CREATE OR REPLACE PROCEDURE test_Exception_byLeejin
(
ParameterA IN varchar,
ParameterB IN varchar,
ErrorCode OUT varchar --返回值,错误编码
)
AS
/*以下是一些变量的定义*/
V NUMBER;
V nvarchar();
V NUMBER; 
APP_EXP EXCEPTION; --自定义异常
BEGIN
ErrorCode :='';
IF (ParameterA=ParameterB) THEN
ErrorCode := 'ParameterA = ParameterB';
RAISE APP_EXP; -- 抛出异常
END IF;
EXCEPTION
WHEN APP_EXP THEN --在处理异常
RAISE_APPLICATION_ERROR(-,ErrorCode);
WHEN OTHERS THEN 
RAISE_APPLICATION_ERROR(-,'未知异常');
END;