• 如果想重新安裝mysql必須先卸載老mysql安裝文件。

brew remove mysql  
brew cleanup  
launchctl unload -w ~/Library/LaunchAgents/com.mysql.mysqld.plist  
rm ~/Library/LaunchAgents/com.mysql.mysqld.plist  
sudo rm -rf /usr/local/var/mysql  

• 下面開始重新安裝mysql，第二句意思是設置mysql為開機啟動項目。

brew install mysql  
ln -sfv /usr/local/opt/mysql/*.plist ~/Library/LaunchAgents  
mysql.server start  

• mysql安裝完畢。下面配置密碼信息；
  mysql -uroot

select user,password,host from mysql.user;  
delete from mysql.user where user='';  
delete from mysql.user where host='::1';  
set password for root@localhost=password('123456');  
GRANT ALL PRIVILEGES ON *.* TO 'miaohr'@'%'  IDENTIFIED BY '123456';  
flush privileges;  

• 如果想修改mysql的配置，在/usr/local/etc下建立一個my.cnf，例如增加log

[mysqld]  
general-log  
general_log_file = /usr/local/var/log/mysqld.log  

• mysql.server restart