大家肯定听说过,有些开发者由于个人失误,在delete或者update语句的时候没有添加where语句,导致整个表数据错乱。
mysql安全模式:mysql发现delete、update语句没有添加where或者limit条件时会报错。整个sql将无法执行,有效防止了误删表的情况。
在mysql中通过如下命令查看状态:
show variables like 'sql_safe_updates';
默认是OFF状态,将状态设置为ON即可:
set sql_safe_updates=1;
//打开set sql_safe_updates=0;
//关闭设置为ON之后
打开安全模式进行测试
delete from t_user
delete from t_user > 1175 - You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column > 时间: 0.001s
update t_user set name='123'
update t_user set name='123' > 1175 - You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column > 时间: 0.001s
delete from t_user where name='123'
delete from t_user where name='123' > 1175 - You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column > 时间: 0.007s
如果delete的where条件不是索引键,则必须要添加limit才可以。
delete from t_user where name='123' limit 1
delete from t_user where name='123' limit 1 > Affected rows: 0 > 时间: 0.002s
delete from t_user where group_id='123'
delete from t_user where group_id='123' > Affected rows: 0 > 时间: 0s
如果设置了sql_safe_updates=1
,那么update
语句必须满足如下条件之一才能执行成功
delete
语句必须满足如下条件之一才能执行成功