Microsoft SQL Server - Transactions
This article describes transactions in Microsoft SQL Server 2008 and earlier.
In SQL Server, transactions are explicit by default. This means that each SQL statement is not a part of a logical transaction by default, and it is committed on completion.
To start a transaction in SQL Server, you have to run BEGIN TRANSACTION (or BEGIN TRAN) statement. The transaction ends with a corresponding COMMIT TRANSACTION (or COMMIT TRAN) or ROLLBACK TRANSACTION (or ROLLBACK TRAN) statements.
Applications (JDBC, ODBC i.e.) can set Autocommit off to use implicit transactions, and to not commit each statement on completion.
SQL Server - Transactions in Other Databases