Mysql safety update 安全模式【 更新或删除数据操作】

在mysql中，如果在update和delete没有加上where条件，数据将会全部修改。不只是初识mysql的开发者会遇到这个问题，工作有一定经验的工程师难免也会忘记写入where条件。为了避免失误造成的数据全部修改和删除，可开启mysql的安全模式。

（1）、查询安全模式是否开启

连接到数据库后，查看当前mysql的安全模式的状态

mysql> show variables like 'sql_safe_updates';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| sql_safe_updates | OFF   |
+------------------+-------+
1 row in set (0.00 sec)

//全局临时生效
set global sql_safe_updates=1;           //安全模式打开状态
set global sql_safe_updates=0;          //安全模式关闭状态

永久生效：先引入init.sql ，再写入全局变量


vim /etc/my.cnf
.....
[mysqld]
init-file=/etc/init.sql
.....

[root@web etc]# vim /etc/init.sql 
set global sql_safe_updates=1;


重启数据库生效
systemctl restart mysqld


mysql> show variables like 'sql_safe_updates';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| sql_safe_updates | ON    |
+------------------+-------+
1 row in set (0.00 sec)

模拟往student 表里插入几条数据，再模拟删除

mysql> select * from student;
+----+--------+-----+---------+---------------------+----------+
| id | sname  | age | sgender | intime              | tel      |
+----+--------+-----+---------+---------------------+----------+
|  1 | fxkjnj |  24 | M       | 2022-02-01 12:14:15 | 11111111 |
|  2 | fxkjnj |  24 | M       | 2022-02-01 12:14:15 | 22222    |
|  3 | fxkjnj |  24 | M       | 2022-02-01 12:14:15 | 33333    |
|  4 | fxkjnj |  24 | M       | 2022-02-01 12:18:16 | 3333     |
+----+--------+-----+---------+---------------------+----------+
4 rows in set (0.00 sec)

mysql> delete from student;
ERROR 1175 (HY000): You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column. 
mysql> 

mysql> select * from student;
+----+--------+-----+---------+---------------------+----------+
| id | sname  | age | sgender | intime              | tel      |
+----+--------+-----+---------+---------------------+----------+
|  1 | fxkjnj |  24 | M       | 2022-02-01 12:14:15 | 11111111 |
|  2 | fxkjnj |  24 | M       | 2022-02-01 12:14:15 | 22222    |
|  3 | fxkjnj |  24 | M       | 2022-02-01 12:14:15 | 33333    |
|  4 | fxkjnj |  24 | M       | 2022-02-01 12:18:16 | 3333     |
|  5 | fxkjnj |  24 | M       | 2022-02-01 12:22:21 | 23333    |
+----+--------+-----+---------+---------------------+----------+
5 rows in set (0.00 sec)

mysql> update student set age=25;
ERROR 1175 (HY000): You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column