A transaction is a single unit of work. If a transaction is successful, all of the data modifications made during the transaction are committed and become a permanent part of the database. If a transaction encounters errors and must be canceled or rolled back, then all of the data modifications are erased.
SQL Server operates in the following transaction modes:
Autocommit transactions
Each individual statement is a transaction.
Explicit transactions
Each transaction is explicitly started with the BEGIN TRANSACTION statement and explicitly ended with a COMMIT or ROLLBACK statement.
Implicit transactions
A new transaction is implicitly started when the prior transaction completes, but each transaction is explicitly completed with a COMMIT or ROLLBACK statement.
Batch-scoped transactions
Applicable only to multiple active result sets (MARS), a Transact\-SQL explicit or implicit transaction that starts under a MARS session becomes a batch-scoped transaction. A batch-scoped transaction that is not committed or rolled back when a batch completes is automatically rolled back by Transact\-SQL SQL Server
[!NOTE] For special considerations related to Data Warehouse products, see Transactions (SQL Data Warehouse).
SQL Server provides the following transaction statements:
| BEGIN DISTRIBUTED TRANSACTION | ROLLBACK TRANSACTION |
| BEGIN TRANSACTION | ROLLBACK WORK |
| COMMIT TRANSACTION | SAVE TRANSACTION |
| COMMIT WORK |
SET IMPLICIT_TRANSACTIONS (Transact-SQL)
[@@TRANCOUNT (Transact-SQL)](../../t-sql/functions/trancount-transact-sql.md)