What is the scope of TRANSACTION in Sql server

Question

I was creating a stored procedure and I see some differences between my methodology and my colleague's.

I am using SQL Server 2005

1. My Stored procedure looks like this

   BEGIN TRAN
       BEGIN TRY
           INSERT INTO Tags.tblTopic 
               (Topic, TopicCode, Description)
               VALUES(@Topic, @TopicCode, @Description)
   
           INSERT INTO Tags.tblSubjectTopic
               (SubjectId, TopicId)
               VALUES(@SubjectId, @@IDENTITY)
         COMMIT TRAN
   END TRY
   
   BEGIN CATCH
           DECLARE @Error VARCHAR(1000)
           SET @Error= 'ERROR NO : '+ERROR_NUMBER() + ', LINE NO : '+ ERROR_LINE() + ', ERROR MESSAGE : '+ERROR_MESSAGE()
           PRINT @Error
           ROLLBACK TRAN
   END CATCH
   
   
   

2. And my colleague's way of writing looks like the below one

   BEGIN TRY
       BEGIN TRAN
           INSERT INTO Tags.tblTopic 
               (Topic, TopicCode, Description)
               VALUES(@Topic, @TopicCode, @Description)
   
           INSERT INTO Tags.tblSubjectTopic
               (SubjectId, TopicId)
               VALUES(@SubjectId, @@IDENTITY)
      COMMIT TRAN
   END TRY
   
   BEGIN CATCH
           DECLARE @Error VARCHAR(1000)
           SET @Error= 'ERROR NO : '+ERROR_NUMBER() + ', LINE NO : '+ ERROR_LINE() + ', ERROR MESSAGE : '+ERROR_MESSAGE()
           PRINT @Error
           ROLLBACK TRAN
   END CATCH
   
   
   

Here the only difference between the two methods is the position of Begin TRAN. According to me my colleague's method should not work when an exception occurs i.e. Rollback should not get executed because TRAN doesn't have scope in method 2. But when I tried to run both the methods, they were working in the same way.

In Method 1, scope of TRAN is outside of try block so it should be visible in both try block and catch block and should give result as per the scope methodology of programming works.

In Method 2, scope of TRAN is limited within Try block so Commit and Rollback should occur within the try block and should throw exception when a Rollback with no Begin Tran exists in catch block, but this is also working perfectly.

I am confused about how TRANSACTION works. Is it scope-free?

Answer 1

Transactions are not "scoped" in the way that programming languages are.

Transactions are nested for the current connection. Each BEGIN TRAN starts a new transaction and this transaction ends whenever a COMMIT or ROLLBACK is called, it does not matter where in your stored proc this is.

Answer 2

Transactions are nested for the current connection. Each BEGIN TRAN starts a new transaction and this transaction ends whenever a COMMIT or ROLLBACK is called, it does not matter where in your stored proc this is.

only to add that ROLLBACK ends "all" open transactions for the connection...