创建触发器

create or replace trigger my_trigger1 
 after insert or delete or update on teachers
declare
 sql_info varchar2(20);
begin
  if inserting then
     sql_info := 'insert';
  elsif updating then sql_info := 'update';
  else sql_info := 'delete';
  end if;
  
  insert into sql_info
  select sql_info from dual;


end my_trigger1;