Can't connect to local MySQL server through socket '/tmp/mysql.sock'

dengzemiaodeMacBook-Pro:~ dengzemiao$ mysql -u root -p
Enter password: 
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)

• 我这里是数据没有启动就进行登录，先确定数据库已经启动，在进行登录数据库。