In SQL Server 2000, we used to handle the errors while performing the DML queries by means of global variable @@Error. These errors may occur due to many reasons like data type mismatch, referential integrity violation etc. The @@error variable tells us whether the last statement (immediate before the @@error variable is used) caused any error or executed successfully. We could check its value for the same. If it is more then 0, then there is some error. But using @error variable & handling the error this way was not handy in solving many problems/requirements. For example if we have multiple DML statements being executed in a sequence and we want to take some action as soon as any of these statements causes any error. In that case after each & every transaction we have to check for @@error variable.
In SQL Server 2005, TRY-CATCH block was introduced to enhance the error handling process of TSQL. In this we can specify a TRY block and can catch the error(s) in CATCH block as caused by any of those queries defined in the TRY block. And this way we can either COMMIT or ROLLBACK them in TRY & CATCH respectively.
Now sometimes we need nested transactions to be configured. Nested transactions mean we may require having some inner transactions with one or more outer transaction. In that scenario, we must have to be very careful in Committing or rolling back the transaction.
Points to be remembered:
- A COMMIT statement in the Outer transaction will commit all the open inner transactions.
- A Commit statement in the Outer transaction will not commit the changes rolled back by the inner transactions.
- A Rollback statement in the Outer transaction will rollover all the inner transaction, irrespective of the Commit/Rollback fired in the inner transaction(s).
SELECT * FROM TESTTABLE
BEGIN TRANSACTION –Outer TRAN
BEGIN TRY
BEGIN TRAN A –INNER TRAN
BEGIN TRY
INSERT INTO TESTTABLE VALUES (11111)
COMMIT TRAN A
END TRY
BEGIN CATCH
ROLLBACK TRAN A
END CATCH
ROLLBACK TRAN –Rollback all
END TRY
BEGIN CATCH
ROLLBACK TRAN
END CATCH
Result:
Though we have committed the inner transaction (‘A’) after insertion, all data got rolled back by the Rollback statement of the outer transaction.
Note: In general, only open transactions can be committed or rolled back. So check it XACT_STATE() <> 0 before commit or rollback.
Tech Updates 
Nice one Munish, but the line
ROLLBACK TRAN A
will cause an error because there is no savepoint named A. A named transaction is not same as a savepoint. You can create a savepoint with:
SAVE TRANSACTION {savepoint-name}
Hey Obiora,
It’s not like the case, In SQL Server 2005, we can also name the transactions as well.
And the above SQL script runs very well.
Thanks,
Munish Bansal
Munish,
I have to disagree with you about the use of transaction naming an a SQL 2005 SPROC. I have the following Stored Procedure:
CREATE PROCEDURE [dbo].[sp_LinkedDatetimeInformation_Insert]
(
@newDetailLinkTableName nvarchar(100),
@newParentId nvarchar(50),
@newParentRecordId bigint,
@newDateTimeTypeCode nvarchar(50),
@newLinkedDetailCode nvarchar(10),
@newRecordedDateTime datetime,
@newTimeQualifier nvarchar(10),
@useTimeQualifierCode bit,
@useTimeValue bit,
@newDetailLinkId bigint = -1 OUTPUT
)
AS
BEGIN
SET NOCOUNT ON;
BEGIN TRANSACTION trn_LinkedDatetimeInfo_Insert
BEGIN TRY
DECLARE @linkedDetailRecordId bigint
exec sp_DatetimeInformation_Insert
@newDateTimeTypeCode,
@newLinkedDetailCode,
@newRecordedDateTime,
@newTimeQualifier,
@useTimeQualifierCode,
@useTimeValue,
@linkedDetailRecordId OUTPUT
INSERT INTO tbl_datetime_information_links
(detailRecordId, tableName, parentRecordId, parentId, linkedDetailCode, recordStatus, linkedRecordHashValue)
VALUES
(@linkedDetailRecordId,
@newDetailLinkTableName,
@newParentRecordId,
@newParentId,
@newLinkedDetailCode,
0x1)
SET @newDetailLinkId = SCOPE_IDENTITY()
IF(@@ROWCOUNT 0)
ROLLBACK TRANSACTION trn_LinkedDatetimeInfo_Insert
RAISERROR(@exception_message,@exception_level,@exception_state)
END CATCH
COMMIT TRANSACTION trn_LinkedDatetimeInfo_Insert
END
Which raises an error that the trn_LinkedDatetimeInfo_Insert cannot be rolled back because there is not a transaction of that name. I realize that we can name transactions, but I do not think that the naming works correctly with nested transactions. I haven’t looked into this much further than doing a google search, but I continue to get the error regardless of where I open the transaction (in the try, out of the try, etc..) Maybe I am missing something?
For some reason the SQL that I pasted in was corrupted.
I have repasted below, but I am not sure why it was corrupted to begin with…
CREATE PROCEDURE [dbo].[sp_LinkedDatetimeInformation_Insert]
(
@newDetailLinkTableName nvarchar(100),
@newParentId nvarchar(50),
@newParentRecordId bigint,
@newDateTimeTypeCode nvarchar(50),
@newLinkedDetailCode nvarchar(10),
@newRecordedDateTime datetime,
@newTimeQualifier nvarchar(10),
@useTimeQualifierCode bit,
@useTimeValue bit,
@newDetailLinkId bigint = -1 OUTPUT
)
AS
BEGIN
SET NOCOUNT ON;
BEGIN TRANSACTION trn_LinkedDatetimeInfo_Insert
BEGIN TRY
DECLARE @linkedDetailRecordId bigint
exec sp_DatetimeInformation_Insert
@newDateTimeTypeCode,
@newLinkedDetailCode,
@newRecordedDateTime,
@newTimeQualifier,
@useTimeQualifierCode,
@useTimeValue,
@linkedDetailRecordId OUTPUT
INSERT INTO tbl_datetime_information_links
(detailRecordId, tableName, parentRecordId, parentId, linkedDetailCode, recordStatus)
VALUES
(@linkedDetailRecordId,
@newDetailLinkTableName,
@newParentRecordId,
@newParentId,
@newLinkedDetailCode,
0x1)
SET @newDetailLinkId = SCOPE_IDENTITY()
IF(@@ROWCOUNT 0)
ROLLBACK TRANSACTION trn_LinkedDatetimeInfo_Insert
RAISERROR(@exception_message,@exception_level,@exception_state)
END CATCH
COMMIT TRANSACTION trn_LinkedDatetimeInfo_Insert
END
Did it again… sorry,
Basically when an exception occurs in the procedure the CATCH block is not recognizing my Transaction and therefore will not roll it back without an error. (Seems to be getting rolled back by the outer transaction)
Please suggest me the result in following scenario:
Begin Trans Temp
while(i<10)
Begin
Insert into tbltemp values(a,b)
RollBack Trans Temp
End
Commit Trans Temp
Or
Begin Trans Temp
while(i<10)
Begin
Insert into tbltemp values(a,b)
Commit Trans Temp
End
RollBack Trans Temp
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