我写的触发器错在哪？

[jjaacc]

create trigger t1
on authors
for insert
as
declare @name char(20)
select @name=i.au_lname from inserted i
print @name
if exists(select * from authors where au_lname=@name)
begin
raiserror('wrong',16,1) /*为什么老是执行这里？数据库里并没有我插入的数据*/
rollback transaction
end

插入：
insert into authors values('123-12-1232','csq','cc','234 233-2324','dsaf','ss','CA','23422',1)

[j9988]

exists(select * from authors where au_lname=@name)
后触发器啊,它永远都存在.exists永远为真

[j9988]

if exists(select 1 from authors where au_lname=@name group by au_lname having(count(*)>1))--如果有两条记录