MySQL -U防止人为误操作

在很多时候操作数据库的时候，可能领导或DBA登陆了数据库，在执行update和delete时，忘记了加where，可能会导致清空表的悲剧，所以-U的好处就体现了。

1、mysql -U的帮助说明

-U, --safe-updates Only allow UPDATE and DELETE that uses keys.
-U, --i-am-a-dummy Synonym for option --safe-updates, -U.
在mysql命令加上选项-U后，当发出没有WHERE或LIMIT关键字的UPDATE或DELETE时，mysql程序就会拒绝执行

2、指定-U登陆测试

[root@db111 ~]# mysql -uroot -p123 -S /data/3306/mysql.sock -U
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 14
Server version: 5.5.32-log MySQL Community Server (GPL)
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
mysql> delete from erlianzhang.test;
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> quit
Bye

　　不加条件就无法删除，这样就保护了数据，防止误操作。

3、防止领导或DBA误操作

[root@db111 ~]# alias mysql='mysql -U'
[root@db111 ~]# mysql -uroot -p123 -S /data/3306/mysql.sock
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 15
Server version: 5.5.32-log MySQL Community Server (GPL)
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
mysql> delete from erlianzhang.test;
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> delete from erlianzhang.test where Sno=5;
Query OK, 1 row affected (0.02 sec)
mysql> quit
Bye
[root@db111 ~]# echo "alias mysql='mysql -U'" >>/etc/profile
[root@db111 ~]# . /etc/profile
[root@db111 ~]# tail -1 /etc/profile
alias mysql='mysql -U'

　　结论：在mysql 命令后加上-U参数后，当发出没有WHERE或LIMIT关键字的UPDATE或DELETE时，mysql程序拒绝执行，防止误操作给自己找麻烦。

转载至：http://blog.51cto.com/oldboy/1321061