不是插入的触发器不执行if语句corectly

Question

我有我的数据库中的触发器，防止进入一个特定的用户，并停止用户进入同一个问题两次：

create trigger [dbo].[question] 
on [dbo].[Online_Questions] 
instead of insert 
as 
if SYSTEM_USER = 'John' 
begin 
raiserror('You have not paid up your fee',16,1) 
rollback transaction 
end 
if exists(select 1 
    from Online_Questions a, inserted b where a.UserName = b.UserName 
    and a.Question_ID = b.Question_ID) 
begin 
raiserror('You have already submitted this question',16,1) 
rollback 
end 
go 

它成功地阻止约翰进入，但是无论Question_ID如何，它都会阻止任何人进入两次。

例如：

execute as login = 'Tom'; 

insert into Online_Questions (UserName, Question_ID, Answer) 
values (user, 'Q097', 'D'); 

，然后作为触发已经阻止了插入件

insert into Online_Questions (UserName, Question_ID, Answer) 
values (user, 'Q087', 'D'); 

将返回一个错误。

我不明白为什么这是因为if语句检查是否存在用户名和question_ID？

有什么建议吗？

Answer 1

我已经知道我要出错的地方，它的格式不正确，看着两张表。这是解决方案。

create trigger [dbo].[question] 
on [dbo].[Online_Questions] 
instead of insert 
as 
if SYSTEM_USER = 'John' 
begin 
raiserror('You have not paid up your fee',16,1) 
return 
end 
if (not exists (select oq.UserName, oq.Question_ID from Online_Questions oq, inserted i where oq.UserName = i.UserName and oq.Question_ID = i.Question_ID)) 
begin 
insert into Online_Questions 
select User, Question_ID, Answer 
from inserted 
end 
else 
begin 
raiserror('You have already submitted this question',16,1) 
end 
go