No Lock in sql server means what

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What is the meaning of the (Nolock) in sql server and pls explain with an example ?

Posted 17-Aug-12 18:29pm

lalitkr

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5 solutions

Solution 5

You have given many good links already, but I would suggest also going through this article What should be considered when NOLOCK hint is used[^]

Posted 19-Aug-12 1:56am

Wendelius

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Espen Harlinn 19-Aug-12 8:29am

Nice link :-D

Wendelius 19-Aug-12 8:31am

Thanks, couldn't resist :)

Solution 3

When you use the NOLOCK query hint you are telling the storage engine that you want to access the data no matter if the data is locked by another process or not.
Reference Link :- What does WITH (NOLOCK) actually mean[^]

Posted 17-Aug-12 19:42pm

RaviRanjanKr

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Espen Harlinn 19-Aug-12 8:30am

5'ed!

RaviRanjanKr 20-Aug-12 1:05am

Thanks :)

Solution 1

http://www.delphigroups.info/2/9c/245233.html[^]

Posted 17-Aug-12 18:45pm

Nileshbhai

Solution 4

Kindly refer the below link:

Use of (NOLOCK) in SQL[^]

Posted 18-Aug-12 0:40am

Arunprasath Natarajan

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Santhosh Kumar Jayaraman · Accepted Answer · 2012-08-17T19:09:00

WITH (NOLOCK) is the equivalent of using READ UNCOMMITED as a transaction isolation level. So, you stand the risk of reading an uncommitted row that is subsequently rolled back, i.e. data never made it into the database. So, while it can prevent reads being deadlocked by other operations.

SQL

SELECT * FROM Employee WITH (READUNCOMMITTED)

this is same as

SQL

SELECT * FROM Employee  WITH NOLOCK

The NOLOCK and READUNCOMMITED hints are only allowed with SELECT statements. If we try to use this for an UPDATE, DELETE or INSERT we will get an error.

Check this link for an example.

http://www.mssqltips.com/sqlservertip/2470/understanding-the-sql-server-nolock-hint/[^]