By default, MySQL starts the session for each new connection with autocommit mode 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 15.19.4, “InnoDB Error Handling”.
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 a
COMMIT before executing the
statement. For details, see Section 14.3.3, “Statements That Cause an Implicit Commit”.