Difference between Implicit and Explicit Transaction

Question

What is the difference between Implicit and Explicit transaction in Sql Server 2008?

What happens in TransactionScope background? I'm using TransactionScope but in Sql server profiler I don't see "Begin transaction..." statement.

How does it work?

Answer 1

• Implicit Transactions: http://msdn.microsoft.com/en-us/library/ms188317.aspx
• SET IMPLICIT_TRANSACTIONS { ON | OFF} http://msdn.microsoft.com/en-us/library/ms187807.aspx

Basically, in c# when you set the TransactionScope to Implicit, it calls the SQL Server SET command to put the connection in IMPLICIT_TRANSACTIONS mode. Anything that you do (using one of the commands listed in the 2nd link) starts a transaction that is kept open until a commit is issued. If no commit is issued at the end of a connection, an implicit ROLLBACK is performed.

This differs from the OFF setting, which also puts every statement into a transaction - the difference is that in the OFF mode (therefore transactions are explicit), each transaction (singular statement) is immediately committed.