SQL Server 2005-如果不存在则插入

互联网上有很多有关此常见问题"的信息.

There is lots of information in the internet regarding this common "problem".

解决方案，例如:

IF NOT EXISTS() BEGIN INSERT INTO (...) END

我认为不是线程安全的，您可能会同意.

are not thread-safe in my opinion and you will probably agree.

但是，您能否确认将现存项放入一个select的where子句中将解决sql引擎中最高并发性的问题? 够了吗?

However could you confirm that putting the exist into the where clause of one single select would solve the problem of the highest concurrency in sql engine? Is it enough?

insert into Table (columns)
select column1, column2, column3
where not exists (select top 1 1 from Table where something)

应该在那里也添加一些更高的交易级别，或者 可以在默认的一个(已提交)上执行吗?

Should be there also added some higher transaction level or can this be executed on a default one: committed?

这项工作会处于未提交的级别吗?

Would this work under uncommitted level?

谢谢！

//稍后添加

我可以假设两个sql都是正确的吗?

Can i assume that both sql' are correct:

1) 设置事务隔离级别可重复读取

1) set transaction isolation level repeatable read

   IF NOT EXISTS() BEGIN INSERT INTO (...) END

2)设置事务隔离级别可重复读取

2) set transaction isolation level repeatable read

insert into Table (columns)
select column1, column2, column3
where not exists (select top 1 1 from Table where something)