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Statement Execution and Transaction Control (139)

原创 Oracle 作者:tsinglee 时间:2007-11-04 11:44:10 0 删除 编辑

A SQL statement that runs successfully is different from a committed transaction.
Executing successfully means that a single statement was:
■ Parsed
■ Found to be a valid SQL construction
■ Run without error as an atomic unit. For example, all rows of a multirow update
are changed.
However, until the transaction that contains the statement is committed, the
transaction can be rolled back, and all of the changes of the statement can be undone.
A statement, rather than a transaction, runs successfully.
Committing means that a user has explicitly or implicitly requested that the changes
in the transaction be made permanent. An explicit request occurs when the user issues
a COMMIT statement. An implicit request occurs after normal termination of an
application or completion of a data definition language (DDL) operation. The changes
made by the SQL statement(s) of a transaction become permanent and visible to other
users only after that transaction commits. Queries that are issued after the transaction
commits will see the committed changes.
You can name a transaction using the SET TRANSACTION ... NAME statement before
you start the transaction. This makes it easier to monitor long-running transactions
and to resolve in-doubt distributed transactions .

语句执行和事务控制
1. SQL语句的成功执行与一个提交的事务的区别在于前者 :
被解析 , 成为一个有效的SQL结构 , 作为一个原子单位运行没有错误 .
2. 提交以为着用户请求对事务中的改变变为永久性 , 修改后的数据对其他用户可见
3. 可以使用SET TRANSACTION ... NAME为事务命名 , 来监控长时间运行和解决拿不准的分布式事务

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