mysql退出命令：\c，强制退出：control+c
bash: mysql: command not found
原因：因为mysql命令的路径在/usr/local/mysql/bin下面,所以直接用mysql命令时,
系统在/usr/bin下面查此命令,所以找不到了。
解决办法：ln -s /usr/local/mysql/bin/mysql /usr/bin/mysql
提示无权限，加sudo。
但是在mac os x ei capitan 系统中加sudo还是提示无权限，
原因：ei capitan中加入了Rootless机制，不再能够随心所欲的读写很多路径下了。设置 root 权限也不行。
解决办法：增加mysql别名
alias mysql=/usr/local/mysql/bin/mysql
同样，也可以给mysqladmin增加一样的别名
alias mysqladmin=/usr/local/mysql/bin/mysqladmin
进入mysql命令行模式
mysql -u root -p
如果看到下面的提示表示已经登录成功。
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 346
Server version: 5.7.11 MySQL Community Server (GPL)
Copyright (c) 2000, 2016, 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>
修改密码和设置有效期
修改mysql 账户密码，修改的是当前登录的帐户密码
SET PASSWORD = PASSWORD('your new password');
ALTER USER 'root'@'localhost' PASSWORD EXPIRE NEVER;
flush privileges;
