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What happens if you don't commit a transaction to a database (say, SQL Server)?
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Closed 9 years ago.
If I Enclose a query between Begin Transaction and commit transaction in MS SQL, what will happen if i abort or stop the execution of the query. Will all the changes that had been done during executing ROLLBACKED.?
Your transaction can remain open until you call something like ROLLBACK TRANSACTION or COMMIT TRANSACTION, or until SQL takes some action on it.
More info:
SQL Server and connection loss in the middle of a transaction
What happens to an uncommitted transaction when the connection is closed?
What happens if you don't commit transaction in a database (say SQL Server)
I actually like to take advantage of this when testing large updates or corrections. You can have something like this:
-- BEGIN TRANSACTION
-- ROLLBACK TRANSACTION
-- COMMIT TRANSACTION
/*
A bunch of SQL code here
*/
Then you can highlight/run the BEGIN TRANSACTION, then run the whole script. If you're happy with the results, you can highlight/run the COMMIT TRANSACTION. If not, run the ROLLBACK TRANSACTION. Since those lines are commented out, they don't affect your overall transaction unless you explicitly highlight and run them.
It depends on your code. As long as your transaction exist, all changes will be pending a rollback or a commit.
You might want to look at this.
No. Transaction will still be active - you didn't rollback after all, did you? :)
Run this example and see what happens. If you break during transaction, you'll see value 2 is in a table, but you have to rollback or commit.
select 1 as x into #xxx
GO
begin transaction
insert into #xxx(x) select 2
-- ctrl+break before time runs out.
waitfor delay '00:00:10'
commit transaction
-- now try this:
select * from #xxx
rollback transaction
select * from #xxx
Related
When try to run SQL transaction from Greenplum. getting this error.
Transaction (Process ID 52) was deadlocked on lock resources with
another process and has been chosen as the deadlock victim.
Rerun the transaction.
We Tried :
On SQL server it is working But we wanted to write same transaction on greenplum
Transaction A
RETRY: -- Label RETRY
BEGIN TRANSACTION
BEGIN TRY
truncate table tablename
WAITFOR DELAY '00:00:05' -- Wait for 5 ms
Insert into tablename
COMMIT TRANSACTION
END TRY
BEGIN CATCH
PRINT 'Rollback Transaction'
ROLLBACK TRANSACTION
IF ERROR_NUMBER() = 1205 -- Deadlock Error Number
BEGIN
WAITFOR DELAY '00:00:00.05' -- Wait for 5 ms
GOTO RETRY -- Go to Label RETRY
END
END CATCH
OUTPUT :
IT INCLUDES
Conversion of mentioned sql transaction (retry and try/catch )block in greenplum syntax.
As process ID keep changing , want to avoid hardcode value when passing into transaction.
3.Also, I am trying to understand this error belongs to SQL SERVER OR transaction we written in greenplum.
Data flow in talend is:
**Read from MS SQL SERVER >> write into hdfs >> load into greenplum**
Any help on it would be much appreciated ?
You cannot begin or end the transaction within a transaction in Greenplum. It auto commit or auto roll back.
Multi-Version Concurrency Control, there is always a data consistency and also query always executes in sequential within parallel mechanisms.
RETRY: -- Label RETRY
BEGIN
truncate table tablename
select pg_sleep(5) -- Wait for 5 ms
Insert into tablename
RAISE INFO 'Rollback Transaction'
IF ERROR_NUMBER = 1205 -- Deadlock Error Number
THEN
select pg_sleep(5) -- Wait for 5 ms
-- Go to Label RETRY
END
I am having a bit of hard time understanding how errors affect the completion of batches and/or transactions.
For instance:
BEGIN TRAN;
SELECT 1/0 AS Error;
ROLLBACK;
BEGIN TRAN;
SELECT 1/1 AS NOError;
COMMIT;
GO
Should not the second transaction succeed even though the first fails? Are not transactions dealt with on one-by-one basis? And what is the role played by batches here?
I was reading about SET XACT_ABORT ON command, and the MSDN says:
When SET XACT_ABORT is ON, if a Transact-SQL statement raises a run-time error, the entire transaction is terminated and rolled back.
If it only fails the containing transaction, why the second transaction is never reached?
I have a chunk of SQL code that has the following format:
SET IMPLICIT_TRANSACTIONS ON
// Insert or Update Statement #1
GO
// Insert or Update Statement #2
GO
IF ##TRANCOUNT > 0 COMMIT TRAN
SET IMPLICIT_TRANSACTIONS OFF
My question: is statement 1 in the same transaction as statement 2 (but that they are in different batches)? I'd believe so based on my reading on Google but I'd like some second opinions.
Thanks!
It depends.
If the both statements are either one of the following :
ALTER TABLE
FETCH
REVOKE
BEGIN TRANSACTION
GRANT
SELECT
CREATE
INSERT
TRUNCATE TABLE
DELETE
OPEN
UPDATE
DROP
then the answer is yes.
Because if the connection is already in an open transaction, the above statements do not start a new transaction.
If, however, Statement 2 is BEGIN TRANSACTION then it will cause two nested transactions to open.
http://msdn.microsoft.com/en-us/library/ms187807(v=sql.100).aspx
And the GO command is just a batch separator , it doesn't start a new transaction.
A transaction can be wrapped around multiple batches.
If I have a stored procedure that executes another stored procedure several times with different arguments, is it possible to have each of these calls commit independently of the others?
In other words, if the first two executions of the nested procedure succeed, but the third one fails, is it possible to preserve the results of the first two executions (and not roll them back)?
I have a stored procedure defined something like this in SQL Server 2000:
CREATE PROCEDURE toplevel_proc ..
AS
BEGIN
...
while #row_count <= #max_rows
begin
select #parameter ... where rownum = #row_count
exec nested_proc #parameter
select #row_count = #row_count + 1
end
END
First off, there is no such thing as a nested transaction in SQL Server
However, you can use SAVEPOINTs as per this example (too long to reproduce here sorry) from fellow SO user Remus Rusanu
Edit: AlexKuznetsov mentioned (he deleted his answer though) that this won't work if a transaction is doomed. This can happen with SET XACT_ABORT ON or some trigger errors.
From BOL:
ROLLBACK TRANSACTION without a
savepoint_name or transaction_name
rolls back to the beginning of the
transaction. When nesting
transactions, this same statement
rolls back all inner transactions to
the outermost BEGIN TRANSACTION
statement.
I also found the following from another thread here:
Be aware that SQL Server transactions
aren't really nested in the way you
might think. Once an explict
transaction is started, a subsequent
BEGIN TRAN increments ##TRANCOUNT
while a COMMIT decrements the value.
The entire outmost transaction is
committed when a COMMIT results in a
zero ##TRANCOUNT. But a ROLLBACK
without a savepoint rolls back all
work including the outermost
transaction.
If you need nested transaction
behavior, you'll need to use SAVE
TRANSACTION instead of BEGIN TRAN and
use ROLLBACK TRAN [savepoint_name]
instead of ROLLBACK TRAN.
So it would appear possible.
Suppose I have a stored procedure that manages its own transaction
CREATE PROCEDURE theProc
AS
BEGIN
BEGIN TRANSACTION
-- do some stuff
IF #ThereIsAProblem
ROLLBACK TRANSACTION
ELSE
COMMIT TRANSACTION
END
If I call this proc from an existing transaction, the proc can ROLLBACK the external transaction.
BEGIN TRANSACTION
EXEC theProc
COMMIT TRANSACTION
How do I properly scope the transaction within the stored procedure, so that the stored procedure does not rollback external transactions?
The syntax to do this probably varies by database. But in Transact-SQL what you do is check ##TRANCOUNT to see if you are in a transaction. If you are then you want to create a savepoint, and at the end you can just pass through the end of the function (believing a commit or rollback will happen later) or else rollback to your savepoint.
See Microsoft's documentation on savepoints for more.
Support for savepoints is fairly widespread, but I think the mechanism (assuming there is one) for finding out that you're currently in a transaction will vary quite a bit.
use ##trancount to see if you're already in a transaction when entering