declare @xactid bigint

declare @transactionid nvarchar(28)

select @xactid = transaction_id from sys.dm_tran_current_transaction

select @transactionid = [transaction id] from fn_dblog(null,null) where [Xact ID] = @xactid

select * from fn_dblog(null,null) where [Transaction ID] = @transactionid

 

The [Xact ID] introduced in SQL Server 2008 has the transaction id for the operation LOP_BEGIN_XACT and all the transaction occuring in its context share the common transaction with the [transaction id] column