InnoDB, all user activity occurs inside a
is enabled, each SQL statement forms a single transaction on its
own. By default, MySQL starts the session for each new
enabled, so MySQL does a commit after each SQL statement if that
statement did not return an error. If a statement returns an
error, the commit or rollback behavior depends on the error. See
Section 15.21.5, “InnoDB Error Handling”.
A session that has
enabled can perform a multiple-statement transaction by starting
it with an explicit
statement and ending it with a
statement. See Section 13.3.1, “START TRANSACTION, COMMIT, and ROLLBACK Statements”.
If a session that has
autocommit disabled ends
without explicitly committing the final transaction, MySQL rolls
back that transaction.
Some statements implicitly end a transaction, as if you had done
COMMIT before executing the
statement. For details, see Section 13.3.3, “Statements That Cause an Implicit Commit”.
COMMIT means that the changes
made in the current transaction are made permanent and become
visible to other sessions. A
statement, on the other hand, cancels all modifications made by
the current transaction. Both
InnoDB locks that were set during
the current transaction.
By default, connection to the MySQL server begins with autocommit mode enabled, which automatically commits every SQL statement as you execute it. This mode of operation might be unfamiliar if you have experience with other database systems, where it is standard practice to issue a sequence of DML statements and commit them or roll them back all together.
To use multiple-statement
autocommit off with the SQL statement
= 0 and end each transaction with
appropriate. To leave autocommit on, begin each transaction
TRANSACTION and end it with
The following example shows two transactions. The first is
committed; the second is rolled back.
$> mysql test
mysql> CREATE TABLE customer (a INT, b CHAR (20), INDEX (a)); Query OK, 0 rows affected (0.00 sec) mysql> -- Do a transaction with autocommit turned on. mysql> START TRANSACTION; Query OK, 0 rows affected (0.00 sec) mysql> INSERT INTO customer VALUES (10, 'Heikki'); Query OK, 1 row affected (0.00 sec) mysql> COMMIT; Query OK, 0 rows affected (0.00 sec) mysql> -- Do another transaction with autocommit turned off. mysql> SET autocommit=0; Query OK, 0 rows affected (0.00 sec) mysql> INSERT INTO customer VALUES (15, 'John'); Query OK, 1 row affected (0.00 sec) mysql> INSERT INTO customer VALUES (20, 'Paul'); Query OK, 1 row affected (0.00 sec) mysql> DELETE FROM customer WHERE b = 'Heikki'; Query OK, 1 row affected (0.00 sec) mysql> -- Now we undo those last 2 inserts and the delete. mysql> ROLLBACK; Query OK, 0 rows affected (0.00 sec) mysql> SELECT * FROM customer; +------+--------+ | a | b | +------+--------+ | 10 | Heikki | +------+--------+ 1 row in set (0.00 sec) mysql>
In APIs such as PHP, Perl DBI, JDBC, ODBC, or the standard C
call interface of MySQL, you can send transaction control
statements such as
the MySQL server as strings just like any other SQL statements
INSERT. Some APIs also offer
separate special transaction commit and rollback functions or