我花了整整一晚上才在我的Mac上成功运行MySQL。我陷入了下面的循环中：
iMAC:~ admin$ brew install mysql
Warning: mysql-5.6.16 already installed
iMAC:~ admin$ mysql.server start
Starting MySQL
. ERROR! The server quit without updating PID file (/usr/local/var/mysql/iMAC.local.pid).
iMAC:~ admin$ mysql.server restart
ERROR! MySQL server PID file could not be found!
Starting MySQL
. ERROR! The server quit without updating PID file (/usr/local/var/mysql/iMAC.local.pid).
iMAC:~ admin$ launchctl load ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist
homebrew.mxcl.mysql: Already loaded
iMAC:~ admin$ brew uninstall mysql
Uninstalling /usr/local/Cellar/mysql/5.6.16...
Error: Permission denied - /usr/local/Cellar/mysql/5.6.16
iMAC:~ admin$ brew uninstall mysql --force
Uninstalling mysql...
Error: Permission denied - /usr/local/Cellar/mysql/5.6.16
有什么线索可以使它工作吗？