Comments on: SQL SERVER – Applying NOLOCK Hint at Query Level – NOLOCK for whole Transaction

By: SQL SERVER – Weekly Series – Memory Lane – #025 | SQL Server Journey with SQL Authority

Sat, 20 Apr 2013 01:31:53 +0000

[...] Applying NOLOCK Hint at Query Level – NOLOCK for whole Transaction How do I apply NOLOCK hint to my whole query. I know that I can use NOLOCK at every table level but I have many tables in my query and I want to apply the same to all the tables. Read the answer to the question in this blog post. [...]

By: Fardin

Fardin — Fri, 21 Sep 2012 07:44:11 +0000

I have a process which pulls the data and send SMS. My concern is, if i start inserting the data in the Table from where i read and send sms and the same time i run the application which send sms, it should not read the inserted data until its committed. But in the mean time it should fetch all the previously commited transaction. How can i achieve the save.

BEGIN TRAN A
INSERT INTO test_name VALUES (‘ABC’)

SELECT * FROM test_name (Should return me data other then ‘ABC’ as its not committed yet.

By: shawn

shawn — Fri, 27 Apr 2012 02:38:19 +0000

Thanks! you are a life savor, spent a while trying to figure out how to dynamically add to a generated nhibernate query.

By: SQL SERVER – Locking, Blocking and Deadlock – Quiz – Puzzle – 9 of 31 « SQL Server Journey with SQL Authority

Tue, 10 Jan 2012 01:31:27 +0000

[...] SQL Server Interview Questions and Answers ISBN: 1466405643 Page#56-57 Simple Example of Snapshot Isolation – Reduce the Blocking Transactions TRANSACTION, DML and Schema Locks Introduction to Live Lock – What is Live Lock? Applying NOLOCK Hint at Query Level – NOLOCK for whole Transaction [...]

By: SQL SERVER – Locking and Blocking – Important Aspect of Database and Effect on Performance – Quiz – Puzzle – 5 of 31 « SQL Server Journey with SQL Authority

Fri, 06 Jan 2012 01:31:12 +0000

[...] SQL Server Interview Questions and Answers ISBN: 1466405643 Page#41-43 Simple Example of Snapshot Isolation – Reduce the Blocking Transactions TRANSACTION, DML and Schema Locks Introduction to Live Lock – What is Live Lock? Applying NOLOCK Hint at Query Level – NOLOCK for whole Transaction [...]

By: SQL SERVER – Importance of ANSI ISOLATION Levels in SQL Server Database – Quiz – Puzzle – 1 of 31 « SQL Server Journey with SQLAuthority

Mon, 02 Jan 2012 01:31:09 +0000

[...] and their Relationship with Isolation Level Check the Isolation Level with DBCC useroptions Applying NOLOCK Hint at Query Level – NOLOCK for whole Transaction Simple Example of Snapshot Isolation [...]

By: Anonymous

Anonymous — Fri, 22 Apr 2011 17:19:02 +0000

If you have a long running query, odds are blocking side effect will be observed with NOLOCK. While bypassing locking might sound tempting, sometimes deadlock might be a better alternative

By: Craig

Craig — Tue, 19 Apr 2011 07:18:59 +0000

Yes, I’d be interested to know if there is any impact on a production database when setting NOLOCK isolation level at the transaction level?

If not, could you clarify the need to change it at the end of the query?

Thanks.

By: Ramdas

Ramdas — Mon, 18 Apr 2011 14:17:04 +0000

Hi Pinal,
Most of the situtations where i have used NOLOCK is at the table level on reporting databases (part of Datawarehouse), very rarely use it in OLTP. Interesting viewpoint on using NOLOCK at transaction level.

By: madhivanan

madhivanan — Mon, 18 Apr 2011 10:37:48 +0000

Yes if the tables are locked by that process and they are used in other places

By: deepraj singh

deepraj singh — Sun, 17 Apr 2011 17:38:37 +0000

great penal .very basic step

By: Taha Amin

Taha Amin — Sun, 17 Apr 2011 11:23:49 +0000

no it will not impact the other processes

By: pinaldave

pinaldave — Sun, 17 Apr 2011 11:22:27 +0000

yeah I know that – but the point was to have it for whole transaction and not at individual table level.

By: Sai Pavan Viswanath

Sai Pavan Viswanath — Sun, 17 Apr 2011 10:03:07 +0000

I have similar kind of requirement but I have to query production databases to run some scripts. Is it safe to work with transaction isolation levels on production databases.

Thanks,
Sai Pavan Viswanath

By: Taha Amin

Taha Amin — Sun, 17 Apr 2011 09:37:05 +0000

@Prawin, no it will not impact the other processes

By: Taha Amin

Taha Amin — Sun, 17 Apr 2011 09:36:21 +0000

@Pinal Dave you can use ‘nolock’ like this
SELECT *
FROM AdventureWorks.Sales.SalesOrderDetail as sod with(nolock)
INNER JOIN AdventureWorks.Sales.SalesOrderHeader as soh with(nolock)
ON sod.SalesOrderID = soh.SalesOrderID
ORDER BY sod.ModifiedDate
but it has two drawbacks
1-another tansaction is rolled back while your query still running you will get this exception:
Could not continue scan with NOLOCK due to data movement.
2-another tansaction is rolled back after your query had ended
then you have dirty data

i recomment to use ‘readpast’ as the database engine not consider any locked rows ordata pages when returning results.

By: prawin

prawin — Sun, 17 Apr 2011 07:16:18 +0000

Lets say the query takes a lot of time to execute say 1 hr..then there would be impact in other places right??..
So, What say?

Thanks,
Prawin