mysql事务的基本理解
文章目录
- 1.1 事务整个流程中的关键字
- 1.2 事务提交成功后不可回滚
- 1.3 事务未提交进行全部回滚
- 1.4 事务未提交回滚到某保存点
1.1 事务整个流程中的关键字
关键字
| 关键字 | 说明 |
|---|---|
| begin | # 等于start transaction;表示开始一个事务,建议使用start transaction; |
| savepoint | # 设置保存点,保存点的名字不能以数字开头；正确示例：savepoint aa # 设置保存点为aa |
| rollback | # 回滚事务到事务开始(rollbackup;),或者回滚到某个保存点(rollbackup to 保存点;) |
| commit | # 事务提交,整个事务结束; |
注意事项
注意：不受autocommit在会话模式和全局模式下值的影响;但一定得按照顺序来哈
start transaction;表示开始一个事务,若结束可以用commit命令;只要commit命令提交后,你就得重新执行start transaction;命令哈;
若一个事务中设置了保存点,但是在执行rollback时没有指定保存点,就回到了事务最开始,此时不能再回退到任何一个保存点上了;
若一个事务中设置了多个保存点(aa和bb),若进行rollbackup to aa;后,此时不可能再回到bb保存点了;
1.2 事务提交成功后不可回滚
** 环境准备(我这里是测试环境哈)**
## 创建chenliang库,并进入到chenliang库下面
create database if not exists chenliang character set utf8 collate utf8_general_ci;
show databases like "chenliang";
use chenliang;
## 创建test1表
create table if not exists test1(
id int unsigned not null auto_increment comment"序列",
name varchar(20) not null comment"姓名",
age tinyint unsigned not null comment"年龄",
primary key(id)
)engine=innodb character set utf8 collate utf8_general_ci comment"测试表1";
## 查看test1表的表结构
desc test1;
事务一但提交成功,不可再进行回滚的验证
## 开始事务
mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)
## 往test1表中插入数据,并提交事务
mysql> insert into test1(name,age) values("chenliang01",24);
Query OK, 1 row affected (0.00 sec)
mysql> select * from test1;
+----+-------------+-----+
| id | name | age |
+----+-------------+-----+
| 1 | chenliang01 | 24 |
+----+-------------+-----+
1 row in set (0.00 sec)
mysql> commit;
Query OK, 0 rows affected (0.00 sec)
## 现在想起插入的数据有误(当然可以修改),但是没法进行回滚了哈;
## 回滚事务,看是否会生效
mysql> rollback;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from test1;
+----+-------------+-----+
| id | name | age |
+----+-------------+-----+
| 1 | chenliang01 | 24 |
+----+-------------+-----+
1 row in set (0.00 sec)
## 实践总结
事务一但提交(commit),无法进行回滚;
1.3 事务未提交进行全部回滚
环境准备(我这里是测试环境哈)
## 创建chenliang库,并进入到chenliang库下面
create database if not exists chenliang character set utf8 collate utf8_general_ci;
show databases like "chenliang";
use chenliang;
## 创建test2表
create table if not exists test2(
id int unsigned not null auto_increment comment"序列",
name varchar(20) not null comment"姓名",
age tinyint unsigned not null comment"年龄",
primary key(id)
)engine=innodb character set utf8 collate utf8_general_ci comment"测试表2";
## 查看test2表的表结构；
desc test2;
事务未提交,回滚至事务开始的实践
## 开始1个事务
mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)
## 往test2表中插入数据,不提交事务哈,且查看插入到表中的数据
mysql> insert into test2(name,age) values("cl01",26);
Query OK, 1 row affected (0.00 sec)
mysql> select * from test2;
+----+------+-----+
| id | name | age |
+----+------+-----+
| 1 | cl01 | 26 |
+----+------+-----+
1 row in set (0.00 sec)
## 回滚事务(回滚至事务开始)
mysql> rollback;
Query OK, 0 rows affected (0.01 sec)
mysql> select * from test2;
Empty set (0.00 sec)
## 结束这个事务
mysql> commit; <==提交这个事务（之前的数据已回滚了哈）
Query OK, 0 rows affected (0.00 sec)
mysql> select * from test2; <==查看test2表中的数据
Empty set (0.00 sec)
# 实践总结
事务未提交（commit）可以进行回滚;
1.4 事务未提交回滚到某保存点
环境准备(我这里是测试环境哈)
## 创建chenliang库,并进入到chenliang库下面
create database if not exists chenliang character set utf8 collate utf8_general_ci;
show databases like "chenliang";
use chenliang;
## 创建test3表
create table if not exists test3(
id int unsigned not null auto_increment comment"序列",
name varchar(20) not null comment"姓名",
age tinyint unsigned not null comment"年龄",
primary key(id)
)engine=innodb character set utf8 collate utf8_general_ci comment"测试表3";
## 查看test3表的表结构；
desc test3;
事务未提交,回滚至某个保存点
## 开始事务
mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)
## 往test3表中插入一条数据,并设置保存点"lili"
mysql> insert into test3(name,age) values("lili",24);
Query OK, 1 row affected (0.00 sec)
mysql> select * from test3;
+----+------+-----+
| id | name | age |
+----+------+-----+
| 1 | lili | 24 |
+----+------+-----+
1 row in set (0.00 sec)
mysql> savepoint lili;
Query OK, 0 rows affected (0.00 sec)
## 再往test3表中插入一条数据,设置保存点为"lanlan"
mysql> insert into test3(name,age) values("lanlan",24);
Query OK, 1 row affected (0.00 sec)
mysql> select * from test3;
+----+--------+-----+
| id | name | age |
+----+--------+-----+
| 1 | lili | 24 |
| 2 | lanlan | 24 |
+----+--------+-----+
2 rows in set (0.00 sec)
mysql> savepoint lanlan;
Query OK, 0 rows affected (0.00 sec)
## 回滚至保存点"lili"
mysql> rollback to lili;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from test3;
+----+------+-----+
| id | name | age |
+----+------+-----+
| 1 | lili | 24 |
+----+------+-----+
1 row in set (0.00 sec)
## 提交事务
mysql> commit;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from test3;
+----+------+-----+
| id | name | age |
+----+------+-----+
| 1 | lili | 24 |
+----+------+-----+
1 row in set (0.00 sec)
## 实践总结
事务未提交(commit),可回滚至某个保存点(前提是要设置保存点);