1、先通过：service  mysqld  status  查看mysql是否启动

      （没装mysql service 也可通过 /etc/rc.d/init.d/mysqld status查看）

      若没启动，则启动mysql：service  mysqld  start

2、方法： 修改/etc/my.conf:
[mysqld]
datadir=/usr/local/mysql/data

socket=/var/lib/mysql/mysql.sock

[mysql.server]
user=mysql
basedir=/usr/local/mysql

If there is not currently a section called [client], add one at the bottom of the file and copy the socket= line under the [mysqld] section such as:

[client]
socket=/var/lib/mysql/mysql.sock
（注意：红色标记部分文件路径必须相同）

发现依旧如此，运行/etc/init.d/mysql start报错：Starting MySQLCouldn‘t find MySQL manager or server
是mysqld服务没启，运行/usr/local/mysql/bin/mysqld_safe &

连接mysql出现错误：Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.soc