《MySQL必知必会》第二十六章：事务处理

@author: Tobin
@date: 2019/11/7 17:27:01

事务处理用来维护数据库的完整性，保证成批的MySQL操作要么不执行，要么都执行。
InnoDB支持事务处理。

ROOLBACK：回退。不能回退CREATE和DROP

SELECT * FROM ordertotals;
START TRANSACTION;
DELETE FROM ordertotals;
SELECT * FROM ordertotals;
ROOLBACK;
SELECT * FROM  ordertotals;

COMMIT：类比写回，如果语句执行有部分不成功，就不会执行

START TRANSACTION;
DELETE FROM order_items WHERE order_num = 20010;
DELETE FROM orders WHERE order_num = 20010;
COMMIT;

SAVEPOINT：保留点，部分回退

SAVEPOINT delete1;
ROOLBACK TO delete1;

默认的MySQL语句是自动提交所有更改的。
不默认提交使用下面的语句。

SET autocommit = 0;