SET IMPLICIT_TRANSACTIONS (T-SQL)

Sets implicit transaction mode for the connection.

Syntax

SET IMPLICIT_TRANSACTIONS {ON | OFF}

Remarks

When ON, SET IMPLICIT_TRANSACTIONS sets the connection into implicit transaction mode. When OFF, it returns the connection to autocommit transaction mode.

When a connection is in implicit transaction mode and the connection is not currently in a transaction, executing any of the following statements start a transaction:

If the connection is already in an open transaction, the statements do not start a new transaction.

Transactions that are automatically opened as the result of this setting being ON must be explicitly committed or rolled back by the user at the end of the transaction. Otherwise, the transaction and all the data changes it contains are rolled back when the user disconnects. After a transaction is committed, executing one of the statements above starts a new transaction.

Implicit transaction mode remains in effect until the connection executes a SET IMPLICIT_TRANSACTIONS OFF statement, which returns the connection to autocommit mode. In autocommit mode, all individual statements are committed if they complete successfully.

The Microsoft OLE DB Provider for SQL Server and the SQL Server ODBC driver automatically set IMPLICIT_TRANSACTIONS to OFF when connecting. SET IMPLICIT_TRANSACTIONS defaults to OFF for connections from DB-Library applications.

When SET ANSI_DEFAULTS is ON, SET IMPLICIT_TRANSACTIONS is enabled.

The setting of SET IMPLICIT_TRANSACTIONS is set at execute or run time and not at parse time.

Examples

This example demonstrates transactions that are started explicitly and implicitly with the IMPLICIT_TRANSACTIONS set ON. It uses the @@TRANCOUNT function to demonstrate open and closed transactions.

USE pubs

GO

CREATE table t1 (a int)

GO

INSERT INTO t1 VALUES (1)

GO

PRINT 'Use explicit transaction'

BEGIN TRAN

INSERT INTO t1 VALUES (2)

SELECT 'Tran count in transaction'= @@TRANCOUNT

COMMIT TRAN

SELECT 'Tran count outside transaction'= @@TRANCOUNT

GO

PRINT 'Setting IMPLICIT_TRANSACTIONS ON'

GO

SET IMPLICIT_TRANSACTIONS ON

GO

PRINT 'Use implicit transactions'

GO

-- No BEGIN TRAN needed here.

INSERT INTO t1 VALUES (4)

SELECT 'Tran count in transaction'= @@TRANCOUNT

COMMIT TRAN

SELECT 'Tran count outside transaction'= @@TRANCOUNT

GO

PRINT 'Use explicit transactions with IMPLICIT_TRANSACTIONS ON'

GO

BEGIN TRAN

INSERT INTO t1 VALUES (5)

SELECT 'Tran count in transaction'= @@TRANCOUNT

COMMIT TRAN

SELECT 'Tran count outside transaction'= @@TRANCOUNT

GO

SELECT * FROM t1

GO

-- Need to commit this tran too!

DROP TABLE t1

COMMIT TRAN

GO

See Also