Fun with Transactions - Part IV

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Fun with Transactions - Part IV

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SQLRNNR SSC Guru Points: 281334 More actions · Answer 1

Thanks for the question.

Jason...AKA CirqueDeSQLeil
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I have given a name to my pain...MCM SQL Server, MVP
SQL RNNR
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deepak.a SSCertifiable Points: 5330 More actions · Answer 2

deepak.a

SSCertifiable

Points: 5330

September 24, 2010 at 3:50 am

#1226799

Thanks for the nice Question 🙂

tilew-948340 Hall of Fame Points: 3431 More actions · Answer 3

thank you for the question and thanks to all the people that gived more examples to explain it because I have read the microsoft explanation but my comprehension of it was somewhat wrong

Hardy21 SSCrazy Eights Points: 9708 More actions · Answer 4

Hardy21

SSCrazy Eights

Points: 9708

September 26, 2010 at 11:39 pm

#1227513

Good series of questions Nakul. Thanks

Thanks

amit_adarsh Ten Centuries Points: 1273 More actions · Answer 5

amit_adarsh

Ten Centuries

Points: 1273

November 29, 2010 at 10:15 pm

#1256583

Perfect explanation and example .

🙂

tejaswini.patil SSCommitted Points: 1792 More actions · Answer 6

Hi,

I am little confused.

From the code given for Fun with Transactions - Part III, I learned that we can commit inner transaction and then rollback/ commit outer transaction.

----------------------------------------------------------

Fun with Transactions - Part III code :-

CREATE TABLE MyTable (MyId INT IDENTITY (1,1),

MyCity NVARCHAR(50))

BEGIN TRANSACTION OuterTran

INSERT INTO MyTable VALUES ('Boston')

BEGIN TRAN InnerTran

INSERT INTO MyTable VALUES ('London')

COMMIT TRAN InnerTran

ROLLBACK TRANSACTION OuterTran

SELECT * FROM MyTable

DROP TABLE MyTable

----------------------------------------------------------

Where as for Fun with Transactions - Part IV, We cannot rollback inner transaction. Instead of starting a nested transaction the outer transaction was saved to a savepoint and then rollback upto the savepoint. I feel this is not a nested transaction. There is only one transaction which is saved to a savepoint and can be commtted / rolled back upto the save point. Please correct me if I am wrong.

After reading the earlier discussions I am still not clear on how to use nested transactions. Can any one explain?

Thanks.

Nakul Vachhrajani SSChampion Points: 10283 More actions · Answer 7

Hello, Tejaswini!

It's okay to be confused. Not a problem. I appreciate the fact that you asked for more clarification.

The point illustrated by #3 is, in itself the answer to #4.

Part #3 of this series illustrated that a rollback command will rollback the transactions all the way to the outermost transaction. However, this does not mean that one cannot have logical "save points" that allow you to rollback to the most recent/outermost save point, provided the rollback is a conditional rollback. Without a save point, the rollback must go all the way to the outermost transaction - with named transactions, you cannot rollback to an inner transaction without a save point. That is the point illustrated by part #4.

Hence, the following would have worked with respect to Part #4

CREATE TABLE MyTable (MyId INT IDENTITY (1,1),

MyCity NVARCHAR(50))

BEGIN TRANSACTION OuterTran

INSERT INTO MyTable VALUES ('Boston')

BEGIN TRAN InnerTran

INSERT INTO MyTable VALUES ('London')

SAVE TRAN InnerTran

INSERT INTO MyTable VALUES ('Paris')

SELECT *,'Post Save' FROM MyTable

ROLLBACK TRAN InnerTran

SELECT *,'Post Rollback Inner Transaction' FROM MyTable

ROLLBACK TRANSACTION OuterTran

SELECT *, 'Post Rollback Outer Transaction' FROM MyTable

DROP TABLE MyTable

To get more clarity, what I would recommend is to play around with transactions for a while - there can be no better teacher than experience.

Thanks & Regards,
Nakul Vachhrajani.
http://nakulvachhrajani.com

Follow me on
Twitter: @sqltwins

tejaswini.patil SSCommitted Points: 1792 More actions · Answer 8

Thanks for the clarification Nakul. 🙂

And definitely I will do more practice on Transactions.