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Isolation Level

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AskSQLTeam
Ask SQLTeam Question

0 Posts

Posted - 2006-11-17 : 10:24:54

sara writes "Hi,
I have some questions please ask them ASAP:

1- What is the different between REEDCOMMITTED(Row Versioning)
and REEDCOMMITTED(Locking) in Isolation Level Table?

2- Please describe the difference between Locking & DeadLocking.

3- What is the difference between these 2codes(Test2 , Test3):

User1
-- Test 2: READ COMMITTED
-- 3
SET TRAN ISOLATION LEVEL READ COMMITTED
-- 4
SELECT * FROM CUstomers
-- 6
SELECT * FROM CUstomers
----------------------------
-- Test 3: READ COMMITTED (Simulating non-repeatable read)
-- 1
SET TRAN ISOLATION LEVEL READ COMMITTED
-- 2
SELECT * FROM CUstomers
-- 6
SELECT * FROM CUstomers

User2
-- Test 2: READ COMMITTED
-- 1
BEGIN TRAN
-- 2
UPDATE customers set companyname='+'
where customerid='alfki'
-- 5

COMMIT TRAN
----------------------------
-- Test 3: READ COMMITTED (Simulating non-repeatable read)
-- 3
BEGIN TRAN
-- 4
UPDATE customers set companyname='++'
where customerid='alfki'
-- 5
COMMIT TRAN"

spirit1
Cybernetic Yak Master

11752 Posts

Posted - 2006-11-17 : 10:39:46

BOL explains this nicly.

Go with the flow & have fun! Else fight the flow

blog thingie: http://weblogs.sqlteam.com/mladenp

derrickleggett
Pointy Haired Yak DBA

4184 Posts

Posted - 2006-11-18 : 16:08:31

Please send your teacher the following letter:

Dear Professor,

I am a lazy bastard. I have no understanding of basic concepts that would enable me to someday succeed in the IT industry. Instead of trying to figure things out, even the simplest and most mundane exercise questions, I try to get anyone I can find to answer those questions for me. Why? Because, I don't "get it".

Someday, I will probably be able to get a good job making decent money. I have learned to leech on those around me. I can talk a good game. For the unaware, technically challenged, out-of-touch with reality manager, I will be king. At the expense of those around me, I'll be able to steal good money from someone who can't interview as well (BS skills aren't quite as honed as mine) but is otherwise far more qualified.

Please just don't give me any more exercises. You really shouldn't even make me attend class. I'm not interested in learning the theory. I'm not interested in learning how to make something that will last and provide value to the business. I AM the reason IT has a bad name. Why should you give me an A+ though??? Because, my dear, someday the person I BS into giving me a job........might just allow me to be your boss.

Thanks,

Lazy Student #12310293814081

MeanOldDBA
derrickleggett@hotmail.com

When life gives you a lemon, fire the DBA.

jezemine
Master Smack Fu Yak Hacker

2886 Posts

Posted - 2006-11-18 : 22:29:46

good one

however, the OP didn't ask for the answers to these questions. they asked us to *ask* them ASAP. So I'll go ahead and honor the request: Sara, can you answer the questions for me please? thanks.

SqlSpec - a fast, cheap, and comprehensive data dictionary generator for
SQL Server 2000/2005 and Analysis Server 2005 - http://www.elsasoft.org

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