WITH (NOLOCK) vs SET 事务隔离级别读取未提交 [英] WITH (NOLOCK) vs SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

问题描述

有人可以指导我什么时候使用 WITH (NOLOCK) 而不是 SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

Could someone give me some guidance on when I should use WITH (NOLOCK) as opposed to SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

各自的优缺点是什么?使用一种而不是另一种，您是否遇到过任何意外后果?

What are the pros/cons of each? Are there any unintended consequences you've run into using one as opposed to the other?

推荐答案

它们是一回事.如果您使用set transaction isolation level 语句，它将应用于连接中的所有表，因此如果您只想在一个或两个表上使用nolock，请使用它；否则使用另一个.

They are the same thing. If you use the set transaction isolation level statement, it will apply to all the tables in the connection, so if you only want a nolock on one or two tables use that; otherwise use the other.

两者都会给你带来脏读.如果您对此感到满意，请使用它们.如果你不能有脏读，那么可以考虑 snapshot 或 serializable 提示.

Both will give you dirty reads. If you are okay with that, then use them. If you can't have dirty reads, then consider snapshot or serializable hints instead.

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