MySQLtransaction事务安全示例讲解

mysql> show variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit    | ON    |
+---------------+-------+
-- 关闭自动事务
set autocommit = off;

mysql> show variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit    | OFF   |
+---------------+-------+

-- 客户端A关闭自动事务后操作数据
mysql> select * from my_class;
+----+--------+
| id | name   |
+----+--------+
|  1 | 一班   |
|  3 | 三班   |
+----+--------+
2 rows in set (0.01 sec)
mysql> insert into my_class (name) values('四班');
Query OK, 1 row affected (0.00 sec)

mysql> select * from my_class;
+----+--------+
| id | name   |
+----+--------+
|  1 | 一班   |
|  3 | 三班   |
|  5 | 四班   |
+----+--------+
3 rows in set (0.00 sec)
-- 客户端B看不到新增的 四班数据, 
mysql> select * from my_class;
+----+--------+
| id | name   |
+----+--------+
|  1 | 一班   |
|  3 | 三班   |
+----+--------+
2 rows in set (0.00 sec)

-- 1、开启事务，从这条语句开始，后面所有的语句都不会直接写入到数据表，保存在事务日志中
start transaction 
-- 2、事务处理，多个指令构成
-- 3、事务提交，结束事务
commit / rollback 

mysql> select * from my_class;
+----+--------+
| id | name   |
+----+--------+
|  1 | 一班   |
|  3 | 三班   |
|  5 | 四班   |
+----+--------+
3 rows in set (0.04 sec)
mysql> select * from my_student;
+----+--------+----------+------+--------+
| id | name   | class_id | age  | gender |
+----+--------+----------+------+--------+
|  1 | 刘备   |        1 |   18 |      2 |
|  2 | 李四   |        1 |   19 |      1 |
|  3 | 王五   |     NULL |   20 |      2 |
|  4 | 张飞   |     NULL |   21 |      1 |
|  5 | 关羽   |     NULL |   22 |      2 |
|  6 | 曹操   |        1 |   20 |   NULL |
+----+--------+----------+------+--------+
6 rows in set (0.00 sec)
-- 开启事务
start transaction;
-- 执行事务操作，多个修改操作
insert into my_class (name)values ('六班');
insert into my_student (name, class_id, age, gender)values ('司马懿', 6, 26, 1);
-- 提交事务
commit;
-- 或者回滚操作，所有数据无效清空
rollback;

-- 增加回滚点
savepoint 回滚点名字;
-- 回到回滚点 清空之后所有操作
rollback to 回滚点名字;