触发器入门

--创建触发器
--1,在某表添加一条记录时，提示添加了记录
create table tri(id number, name varchar2(32));
--
create or replace trigger mytrigger1 
after
insert on scott.tri
begin
dbms_output.put_line('添加一条记录');
end;
/
--
set serveroutput on;
insert into tri(id,name) values(2,'andy');
--阻止删除
create or replace trigger mytrigger2
before  delete on scott.tri
begin
if to_char(sysdate,'day') in ('星期天','星期六') then
dbms_output.put_line('今天休息!');
raise_application_error(-20001,'今天不能删');--抛出异常
end if;
end;
/
delete from tri where id=1;
select * from tri;