mysql - 没有 "commit"的单个 "begin transaction"语句

Question

我正在使用带有 mysqldb 适配器的 web2py dal 连接到 mysql 服务器。

我的问题:

1. 为什么在“set autocommit=0”之后需要一个“commit”而不是“begin transaction”
2. 如果 autocommit=0，“select”语句是否开始事务？

服务器信息:Innodb引擎自动提交=1(默认值)tx_isolation=repeatable-read(默认值)

一般日志:

100356 10:00:00 123456 Connect  dummy@172.0.0.1 on dummydb
123456 Query    SET NAMES 'utf8'
123456 Query    SET AUTOCOMMIT = 0
123456 Query    COMMIT
123456 Query    SET FOREIGN_KEY_CHECKS=1
123456 Query    SET sql_mode='NO_BACKSLASH_ESCAPES'

Answer 1

呃...因为你禁用了自动提交？？？？

这里有一个很好的解释:

http://rpbouman.blogspot.com/2007/02/mysql-transactions-and-autocommit.html

With autocommit enabled, every statement is wrapped within its own transaction. Successful execution of a statement is implicitly followed by a COMMIT, and the occurrence of an error aborts the transaction, rolling back any changes.

By default, autocommit is enabled in MySQL.

换句话说:

1. “交易”不一定只是“将多个语句作为一个原子实体执行”

2. 自动提交给您一个语句 == 1 个事务的“错觉”

3. 事实上，“automcommit off”为您提供了“一个语句 == 0 个事务”

来自同一个链接:

... The whole point of having autocommit off is that you can issue multiple statements and commit them all at once.