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WITH (NOLOCK) vs SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED Ask Question

tag-icon • tag-icon sql sql-server sql-server-2005
WITH (NOLOCK) vs SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED Ask Question

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

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

ベストアンサー1

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.

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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